sealing slate with impregnator pro

I have approx 1,000 sf of 6x6 black slate Tiles (http://www.g682.net) in my home, kitchen area was becoming very worn as well as having some efflorescence showing.

When we purchased the home the seller told us that the floors had 2 coats of Nulife sealer? Apparently a lacquor sealer.

We hired a contractor to strip and (http://maplered.com) re seal the floors. They used Stone (http://g603.net) tech bulletproof sealer, which looks fine everywhere except where where the old finish was almost completely worn off. In those areas it looks terrible.

My question is, can we put down a lacquor finish over the bulletptoof sealer or do I need to strip it again, before applying the lacquor finish.

The contractor has not been back by to inspect the finish yet, but I expect them to try to minimalize the problem with some sort of excuse as to why it looks so bad.