Ive only dipped in and out of the thread over the 200 pages but seen this sort of comment a few times and it isn't quite true. There are three bits to the article 5.
A) which applies to the club (not its shareholders so far as I can tell). So CPFC itself. This does not apply here, the club dont own any interest in Lyon.
B) which applies to management/administration, which may apply to Textor, not clear to me whether he had any actual involvement in Palace management/admin. Clearly from his role at Lyon he was there. If he was at Palace too (which we'd argue against) Then we'd be out. I haven't got the impression this is what UEFA are arguing but I haven't looked at anything from uefa. But if he was a director (which looks like he was) Then it's probably a slam dunk for uefa.
C)
which applies to shareholders etc and does refer to control or influence and uses examples (not definitive) of control such as majority share ownership when it comes to voting rights (not relevant here) and also being able to exercise a decisive influence in decision making of the club.
So if c is being applied there is scope for arguing what decisive is, it is very relevant how many votes he has etc. I dont see why we wouldn't have a decent chance of appeal tbh even without Textor selling, but obviously the club is paying someone lots of money to advise on that and weigh up if its better to just get on with life now and maybe sue UEFA later.
documents.uefa.com