The "high RAM" at 06xxxxxx has no waitstate penalty - the SH-2 can burst-fetch it at full speed (which is why program code is always stored there). The "low RAM" at 2xxxxxxx does have 1 or 2 waitstates, I forget how many now. Video and sound RAM and register accesses have varying amounts of wait states as well.
of course being SH2 you have the whole cache thing confusing it even more, so if you don't actually hit the ram there is no penalty etc. Implementing universal wait states might just make it too slow.
then of course the dual CPUs. Are any of these tests being done with it set to *perfect* interleave? I have a feeling you're going to find a lot of Saturn games which are fussier than anything on ST-V.