There's been a change in the US coaching staff this season, plus also I think they may well have reallocated a lot of the resources towards the women with Bailey and Burke both retiring, seeing Dunklee as their most likely source of results going forward. Certainly a 31-year-old making that kind of leap in her skiing performance feels like it may be something that would be best served discussed in a different part of the forum, and she - like Kikkan Randall did in XC - has taken up a role as an athlete spokesperson so she puts her head above the anti-doping parapet too. Whether she would make the XC team was not what we were discussing though - it was whether comparing her performances while still an XC skier were a valid stick to beat biathletes with because she's competitive among biathletes now. I think it isn't, because this year's performance is so far out of line with her career to date, and we had several years' worth of performances as a biathlete before these improvements. If she'd gone straight from where she was in XC to the top 15 ski times in biathlon then your point would be valid, but she didn't. She moved to biathlon because she was uncompetitive as an XC skier, but she was then uncompetitive as a skier among biathletes too, for three years, and then made a huge step forward, whatever the reason for that may be. Otherwise it's like pointing at Chris Froome's performances at the Giro del Capo and saying that it proves Kenny de Ketele could be a GT champion, because Froome at some point after that made a huge leap in his performance capabilities that made his Giro del Capo performances no longer relevant as a comparison for his level.
No, Egan isn't a better XC skier than Diggins or Bjornsen or Caldwell or Brennan. But six years ago the 11th fastest biathlete in the world could finish 24th in a World Championships 10k as an XC skier, the level may be a bit lower now with a few retirements of long term fast athletes, and Brennan right now is 37th in the World Cup as the 4th US athlete. The other problem is that we're limited in which events can be reasonably used as a measuring stick, because there's neither an equivalent to the sprint nor an equivalent to the 30k in the biathlon programme. Theresa Stadlober and Nathalie von Siebenthal are 20th and 30th respectively on the World Cup but both can be counted on to be lower end top 10 of any race of long distance, whereas the similar distances of biathlon races means the variety of the names at the front is more caused by variation in shooting, and so you wouldn't expect the biathletes to compete at a level with the XC specialists in sprints, 30ks or any distance in classic technique, so we're really restricted to the 10/15 free as a comparison point.
The argument that biathletes come from failed XC skiers is only valid up to a point. In some countries it is definitely the case. But in other countries - Germany, Czech Republic, Ukraine, Belarus, even to an extent Russia, although in Russia both have traditionally had similarly high regard - biathlon has bigger audiences, bigger funding, and more opportunities (after all, the best XC skiers from many nations will wind up hitting a funding deficit vs. Norway, Sweden and Russia at some point and will not be able to progress any further, whereas there's always the 'shooter's chance' in biathlon where you can win big if others miss the targets - Arnd Peiffer has won an Olympic and World Championship gold the last two seasons by making sure that if the favourites mess up, he's best placed to profit) and even the best XC talent hæmorrhages to biathlon. Because there's always more opportunity in the combination sport. In XC, if you can't beat the Johaugs of this world, you lose. In biathlon, if you're not the fastest skier on the day, you still have a chance if you shoot well and they don't. Vicky Carl has made noises about converting to biathlon, but has abandoned it for the time being. Even Stina Nilsson has been photographed at Östersund doing rifle training a couple of years ago.
My general rule of thumb is that the very best XC skiers wouldn't have any need to go to biathlon (and this is indeed why Stina never bothered taking it beyond a couple of training sessions, because she was that good). The fastest biathletes occasionally get asked to do XC relay legs, because the distances suit them - but not fast enough to justify doing XC full time, which would generally place them towards the 3rd-4th-5th area of a given nation's athletes XC-wise. This varies depending on each nation's relationship between the two sports. The best biathletes in Germany would be faster relative to their XC team (Herrmann and Dahlmeier are up there, I'd wager, with the Carls and Hennigs of this world) than the equivalents in Norway, where XC is preferred (Olsbu and Eckhoff are fast for biathletes and I'd wager they could produce competitive World Cup point-winning performances over the right distance, but anybody who thinks they'd be a match for Johaug or Østberg is crazy). Finland is an outlier because XC is prevalent much more than biathlon, but Kaisa is one of the quickest - however her development of her ski speed came only after she'd been a biathlete for a few years, similar to Egan albeit it happened when she was 27 or so rather than 31.