Those were (are?) the designations for certain types of jobs over there. You might think that if you're hired into the company, your possibilities are wide open, but they aren't. System administrator flavored SREs (site reliability engineers) could only get other SA-flavored jobs, of which there are relatively few. Meanwhile, software engineer (SWE) type SREs could go into any other SWE job, of which there are many.

If you were hired on as a SA-SRE as I was, then you have to do an internal interview to get to be a SWE-SRE. If you can't make it through that, you're stuck. I made it, and a friend did too, but I know people who didn't. I'm sure that makes them feel great, especially if they're already doing SWE type work in their daily jobs.

I was told repeatedly there was no difference between the types, but found out the hard way when it was time to transfer from a toxic situation and there were few alternatives. It took over a year to finally get it all sorted out.