Google is anyway reducing SRE task force & is planning to completely eliminate SRE role. There has been recent announcement already & have already started the move - https://archive.ph/YWp4O
The rare ones that can do a mediocre job at both (and that won't burn out and switch jobs if told to do both) are usually not capable of doing an excellent job at either.
Using analogies from pretty much any other field shows how dumb it is to combine SRE and SWE, or fuse DevOps (or, god forbid DevSecOps) into one rule:
- Would you have a surgeon drive an ambulance?
- An expert car mechanic manage fleet scheduling and logistics?
- Tell a salesman to design marketing graphics, and have your graphic designer manage high-value customer accounts?