Don't think I noticed this in the earlier version... So missed shield attempts get penalized with a 'softer' guard meter? Well at least for HM. Wow.
That's been there. Also Airdodge does it too, regardless of whether the airdodge "did anything" or not, but only half as much as whiffing shields, which I think a lot of people hadn't noticed.
However, in Ver.A, it looks like the guard meter gets weaker much faster, at least for Half Moon. That Akiha player was almost constantly in red just from airdodging, and that was pretty hard to do in the original game.