why Is my bath pooling water on the top edge

Hey there I believe a timber frame of some sort is in fact needed in some cases. Not in all of them. It all depends on the bathtub itself and the overall bathroom condition etc. As for the pooling water, based on your questions and without seeing your bathroom at all. I am guessing, your bathtub is just not leveled. In that case, there probably is a problem with the floor. Again, I can't tell without seeing it :) Hope you will get it fixed!