If you want to argue 'the Encyclopedia Eorzea might be wrong', that's certainly an angle, but we need to admit alternative sources of information in. Not just because we get nothing by just looking at a source and saying 'nuh-uh' with no regard, but also because this isn't a one-source thing; that one source happens to have the most exhaustive explanation, but it's not the only thing saying that LBs are not necessarily using dynamis. And here, the other subjects to consider are that the Ktisis Hyperborea Trust NPCs, and the boss of the Seat of Sacrifice, can all use LBs despite being baseline biologically incapable of manipulating dynamis.
We can't try to bring 'Ktisis' dampener means they can manipulate dynamis' in, either; not only does that have absolutely no evidence to it, but the lines they say alongside these LBs don't imply any surprise in or newness to this situation (well, Hyth is surprised you let him do it, but that's different). In fact, as Lyth pointed out, Emet very directly cites aether as his power source. The Trust Insighters people have actually transcribed every single quote for Venat and Hythlodaeus in all languages (not Emet, for some reason), so you can see for yourself:
https://docs.google.com/spreadsheets...#gid=856154097
No matter what, we're in a state where neither the amount of dynamis and non-dynamis LBs are at 0% or 100%; some LBs cannot possibly be dynamis, while at least one LB, the one against the Endsinger, definitely is (however, again, everything in the Endsinger fight is by nature at least partially dynamis-powered). Where the majority lands depends entirely on whether you think the Encyclopedia Eorzea is mostly accurate. And personally, I think it is, for one simple reason: the most confirmably non-dynamis LBs outside of the Encyclopedia descriptions come from Endwalker. It wouldn't make sense for them to do a blanket, wide-ranging retcon in the exact same content load that they introduced clear exceptions to this supposed 'new fact'.