We noticed occasional water seepage on floor near one of the mounting bolts. I assumed it was a faulty wax seal, so, we removed the toilet bowl, and replaced the seal. We thought the matter was resolved, but, then we observed that especially when there is weight on the toilet, water gushes from this same bolt area on the floor when flushed. Again, it doesn’t do this every time it is flushed, so, I assume there is no stoppage in the drain, and even if so, why would it backup through the drain (and through the seal?) onto the floor rather than the bowl? Any advice is appreciated.

Yes if there is back up, while the seal is water resistant, it is not water tight, and that is one of the places you will see water if there is a back up.
( I know that first hand, I had a plumbing nightmare this weekend)

It may be that the wax seal is not thick enough. There are standard height seals & extended height seals. Suggest you try an extended height seal. If installed properly, there should be no leak under the toilet.

Cheers, Tom