Your story is not completely correct.
Lets talk about three bikes, the ones I have seen at races this season.
1 The one with large tubing, external cable routing different paint job and a white sadle (I suspect its motorized because of results and pushing button)
2 Black bike internal cable with black sadle (I suspect motorized because of results and pushing button)
3 Black bike internal cablewith black sadle
Bike 2 and 3 are very simular and I need good pictures or video to tell the difference. The different print on the saddle is the best give away.
In Zolder she is racing with bike nr 1 and then off track she jumps on bike nr 3.
Bike nr 1 has a broken chain as you can see when she is walking on the finish straight. It can also be seen in this picture:
This suggests bike 2 is the one the UCI took, which is the one from Koppenbergcross. That would explain the in-race situation at least, because if bike 2 had been taken and bike 1 is broken, she probably doesn't have another in the pits, so she needs somebody to go fetch bike 3 from the truck, hence why it's on the outside of the course when she climbs over the barrier to DNF.
We've had conflicting reports on whether the UCI did or didn't check the bike she was riding in the race, which if they didn't surely is an absolutely ridiculous
oversight on their part for many reasons, not least because they publicly stated that she wasn't riding the motorized bike in the race. Yet from Tienus' posts it seems we have reason to suspect bikes 1 and 2 have both been, at some point, motorized. Bike 1 is the one that made Sabrina Stultiens comment, because it's noticeably different to bikes 2 and 3 which are very similar. If they test bike 1 and it's motorized, then the already pretty complicated series of events that need to take place for their excuse to work goes out of the window. That they publicly stated that Femke didn't ride the illegal bike in the race suggests either they didn't test bike 1, or they did and found it clean; in which case, it would suggest Femke has one motor and shifts it from bike to bike accordingly to try to keep people off the scent, presumably wishing to switch to it mid-race, which was not an option once it was confiscated. Certainly she was performing under-par in the race. If they tested it and found it motorized, then they're hiding it to try to protect the integrity of the race (even though Femke was a non-factor) or to try to at least slightly cushion a pretty brutal fall for her.