The tried and true American Association for Acronym Abuse can help there.
This confirms my suspicions - SRE are looked at as inferior or "second class citizens" compared to SWE. It also confirms some of the interviewer bias I experienced (I interviewed for an SRE position).
It's a measurement issue rather than a value judgement. Reliability is "sales we didn't lose due to downtime" while software is "new sales we couldn't have made without THIS GUY RIGHT HERE!".
Though remember, this post was aimed at Google employees, who should know what these are.