I get you, most likely they won't, because they will also not know, that the compliant sub 250 g battery has an imprint. And 40 g more is nearly nothing but yet, if something goes wrong, these 40 g could get you in trouble.
Not worth the risk if you want to keep enjoying A1 open category tbh.
One other thing to remember is that the drone itself probably knows it has a plus battery installed too as it would be heavier and might have slightly different tuning. If RemoteID becomes mainstream, it could easily flag itself as not being under 250g.
Granted, I don't think the Plus battery is worth it. It has not reviewed well from what I've seen and nets maybe half of the rated extra time DJI claims.