no reason for anything... to be honest... i just dont know what the best practice is.
right now i am removing. next step is to lay patterned tile. I will definitely need to know how and the best way.
Gotcha gotcha. Just another DIYer here, but I think the typical practice is to use cement board on top of the plywood subfloor. Or one of the newer membrane products as an alternative. One thing to consider though is that is you add 1/2” cement board for example, the floor height might be different depending on how thick the mortar bed was. This could effect things like height of toilet drain pipe and require a new flange to get extra height, threshold between bathroom and other rooms. Or height could be close to what it was and everything works out with no extra work haha.