I call that job SysOps - caring about systems and operation

SRE just came from the big guys calling their sysadmins SRE

If you look at the history of SRE, it was distinctly NOT sysadmins, Google specifically wanted software engineers hired to automate scaling as well as sysadmin type ops work.

their work is entirely what sysadmins did tho

RCA of complex bugs? Writing infra software?