I generally dislike the B5 stories that get all "things that even Vorlons were not meant to know": I don't like that kind of anti-intellectual attitude in something that's claiming to be SF.

But I think the special is redeemed by the Zack/Lyta scene in the lift: it sort of sums that relationship up that the failure scene was (a) relegated to a spin-off and (b) that it failed because he couldn't even notice that she was blatantly possessed by aliens.