How's this?: If your Pants configuration says:

[python].interpreter_constraints = [">=3.7,<4"]

then that says, you need lockfiles to work with all Pythons convered by that configuration, for example, Python 3.7.4, Python 3.9.10 and Python 3.11b1 (and all the rest <4). SInce the resolve of your requirements runs into a distribution A that itself says it only works with Python in the 3.7 range, that's a conflict. Pants cannot satisfy your request for a lockfile that works with all Pythons covered by

>=3.7,<4

because of that distribution A that has a narrower constraint.