The PFF stint is unusual, as you don't see many young guys leave coaching for multiple years and then come back. It's not a bad thing, but it's not exactly great that he couldn't find a role during that time.
Slowik is 36, and all of his 49ers roles were as an assistant. They don't have an OC in SF because Shanahan does the playcalling, but he really hasn't done a whole lot yet. This was the first year he had the reins to do so, and he did great, but 1 year of OC is pretty unusual to get a HC spot. Kevin O'Connell had 3 years as an OC with 2 different teams before taking the Vikings job. He also won a ring with Matt Stafford at QB. Josh McDaniels had a longer and more decorated resume when he became the Broncos HC at the age of 36. Granted he was the "OC" for Brady and Bellicheck, which is just about the cushiest job you could ask for, but he at least had a few years as an OC and several more as an assistant. It's pretty uncommon to hire a HC that's in his mid-30s, but they typically have at least a few years as a coordinator before that happens. I think Slowik needs about 1-2 years of success at OC before he jumps, so hopefully wins at least 1 Superb Owl before that happens.