Tiling defects - tolerance levels

Hi All, I am in the busy planning stage of choosing a project builder for a new home build.

I am doing research and learning about the building industry and processes. I have a question about the defect identification stage, and I'm particularly interested in people's experiences in identifying floor tiling defects.

I have inspected various display homes with a careful I looking for quality workmanship. When observing the tiling in various display homes, I have noticed the following things:

1) when tapping with my knuckle in the centre of each tile, I noticed that some have a distinct Hollow tapping sound. I know that this is caused by having a concrete void air gap underneath a portion of the tile, which would have been caused by the tiler at the time of laying the tiles.

In terms of the building code, what powers would a client have to ask the Builder to rectify this? would this be considered a defect?

2) I noticed some tiles when butted up against each other that one tile is finished slightly higher than the adjacent tile. Again, same question as above, what tolerances are considered acceptable and what powers does the client have to ask the Builder to rectify this problem?