So given my scenario before, if a PC or creature picked up a magical shield and used it as a serving platter, you are okay with them gaining any magical bonus or feature associated with the magical shield. I mean, they aren't using it in any defensive manner at all, but the magic of the shield helps prevent attacks from hitting them anyway?
Forget the "wording" in the DMG, I agree that is the strict literal meaning, but you are fine with that intent (you seem to be) or are you simply debating that is a reasonable ruling?
But these items must be worn according to their descriptions, and require attunement. So doesn't it seem prone to abuse that a PC without proficiency in shields could just hold a magical shield under their arm and get a magical bonus to their AC?
It seems prone to abuse to me, which is why I take such issue with this SA ruling. I suppose if magical items aren't prevalent in your game, then it is unlikely your front-liners would relinquish a magical shield to a caster just to they could carry it and gain an AC bonus.
If you are simply debating the point but feel otherwise that it seems a strange ruling, we are in agreement.
If you agree with the ruling because your game world (or table) wants magic seen in a more pervasive fashion, then please accept my apologies if my tone and vehemence on the issue caused any offense.
I get heated sometimes when things seem just "wrong to me" and appreciate the Mod stepping in to remind me to keep it civil.