It's very team/org dependent and I would say that's generally not the case. In 6 years I have only had 1 team out of 3 where that was true. The other two teams I was expected to juggle feature work with oncall work. Same for most teams I interacted with.
Interesting, I've been here nearly that long and every team I've worked with its generally the way I described. Do engineers always do that? No. But it is the expectation