Probably the easiest answers are different seat posts, different chain and seat stays..if you ever have ridden some of these bikes majority of them really suck..and longer seat post is way more comfortable, night and day.. Aero seat posts suck..and most aero and TT bikes suck..they are so stiff just beat out your soul and dental work.. And with large cross section wheels, 50s and above bikes can be brutal, harsh is an understatement. Colnago V4 and V5Rs are way easier to ride and don't beat you up, these guys would never put up with any feel like an old Vitus, were you can physically see and feel bottom bracket shell moving when you pedal!! You feel the bike flexing before you even ride it!! So that's the definition of a noodle.. And other bikes from Cervelo and Cipollini with big tubes, stiff stays and aero seatposts are uncomfortable garbage for me personally.. And wheels above 45 for me are uncomfortable and energy and aerodynamic benefits are nullified by discomfort that comes with..
If UAE and Colnago have the the bikes dialed in, you have to assume they do.. You are getting aero- wattage benefits and riders feel like it's comfortable enough and not to heavy to be a liability on moderate climbing. I my assumption on that will possibly be disproved soon if Pogacar and others keep using and winning on a bike that was billed as an aero bike..
Tons of strange stuff has already happened this year with equipment.. @10k uphill time trial and guys come out using TT bikes, don't spend any time with arms in the skis and instead most of the time out on the handles which are same or similar width to regular road bike handlebars... I was puzzled..
I don't know what the feel is of the confluence of toptube, seatpost and then again the unconnected finish of what was the seattube, which Colnago has looking more like a partial rear fender on the Y1Rs..so maybe with all that's going on the bike feels complaint and comfortable.. Which is difficult always.. I personally hate all aero bikes I ridden because they are just too stiff, make me want old soft wheels with no to tire pressure..