Reviewing discussions in the OSM forum (https://community.openstreetmap.org/t/mapping-strip-malls-buildings/109813/43), it looks like the standard is that "strip mall" like retail buildings like this one are normally mapped as one building with poi points for entrances -- like I have already done here. This makes sense as you can't really tell where each unit starts/stops on this building on the ground, nor from aerial images.

I won't change the polygon here and will just keep the points as is. As new businesses open, we'll just have to check what their business licenses says for unit numbers (since they aren't listed on the building itself).