So from what I got out of this is that for pistols it really doesn't matter what the OAL is?
It matters, definitely it matters. I contend however that chambering problems in a handgun are exponentially more likely to be caused by headspace issues than the bullet engaging the lands. So my only recommendation is that before you jump to short OAL's, make sure that's really needed. Verify you're not causing problems due to excessive flare, improper sizing, or insufficient/excessive crimp before you move to changing the OAL. The test you have described is one I utilize as well in setting OAL and still maintaining proper headspace. But because the 9mm is a taper crimp cartridge that headspaces on the mouth, that test is only going to give you an accurate OAL if you're doing those other things correct first. So you want to rule them out first and then adjust your OAL as is needed.