I think we can "solve" this by saying that the list of packages and versions that lsstsw specifies in the conda version pinning file is the list of packages needed as pre-requisites. Then people who aren't on conda can still get at something that can be transformed to a requirements.txt file, and conda users can work out what packages we need (even if that user does not pin). I don't think binary distribution matters at that point.
There is still the other point of when to package in EUPS and when to have a stub EUPS package. That has recently depended on the complexity of the specific package: packages wth minimal dependencies get an EUPS package and complex dependencies have a stub.
I believe I see that EUPS recently had the ability to check for a python package existing from a table file without that python package being an EUPS product.