I am using macro_placement.cfg to place my cells in specific places, but then I get " PHY_185 overlaps <mycell>". Shouldn't those PHY cells be placed in a way that they do not overlap FIXED placed cells?

We've seen this problem if macros aren't properly placed. For example, some are placed and others are not.

I have optimized the placement of my cells now to avoid hitting the PHY's, but for extra large cells that might be unavoidable.