is there a command to say, "build all the python targets where the compatibility requirement is this"? context is one of our targets is only py3.7, and we want to separate the ci command for py3.7 from the rest

Unfortunately no, not at the moment. You'll need to add a redundant

tags={'py37'}

to the target(s) and then use

./pants --tags=[+/-]py37 ...

.

i see

Correct.

-[tag]

excludes targets with the tag,

+[tag]

on includes targets with the tag.