Oh I agree, completely - it's exactly why cargo from SRVs doesn't degrade: absolutely right
The question is whether UA degradation after being carried in a ship is specifically a feature of the UA that has an explanation inside the game rather than a meta-explanation that makes no sense unless you see it as a game.
The suggestion from MB was that the degradation was 'a feature' of the UA. Now, granted: that's vague enough to mean it's a feature it inherits from 'just another cargo item'; but it could also mean that there's an in-game (I.e. story-based) explanation for why UAs degrade after having been dropped from a ship (which there isn't for other cargo).
If there is, then not degrading after being dropped from an SRV might be significant.
That said - if you report it as a bug, and the response is 'by design', then it succeeds in telling us nothing!
I need a rest!