We stayed at the Paradise Pier right after this change & every time we walked from our hotel towards GCH and didn’t appear to be moving along past, security would approach us to ask where we wanted to go & every time we were directed around to the Downtown Disney security stations (we went back for midday breaks so it didn’t really matter if it was before or after 11am). The first time we did try to show them our room keys in case being a Paradise Pier guest made a difference and it did not. So they do generally keep tabs on that intersection & limit the street entrance of the GCH to only GCH-bound guests/diners.
You could use the Downtown Disney security stations & then enter the Grand from the Downtown Disney side to use the DCA entrance & no one would stop you there, but I wouldn’t at all advise that bc you’ll do security 2x, once at Downtown Disney & again as you enter DCA from the Grand.
So short answer: certainly try as the intersection they monitor is on the way to the Downtown Disney security station, but be prepared to walk around. The walk isn’t long & you’re only back-tracking just a tiny bit, but we just find that Downtown Disney can get really really really crowded & much harder to navigate through so we prefer not to have to walk through it.