Minimum Python policy/upgrade policy?

It is. The last toolchain upgrade was mainly feature driven. The update went from C++14 to ++17. The guideline is to support toolchains that are roughly three years old.

3.8 released 2019-10-14.
3.7 released 2018-06-27.

IMHO, an upgrade to 3.8 would be more appropriate. There are several Python tools that would benefit from the features.