I have a friend who left tech after 15 years to go back and get a CS phd. He ended up with a permanent job being the only "software guy" on a team of like exclusively math and physics post-docs. I'm still a little fuzzy on his day-to-day but I think it's basically just having enough of a handle on the research math to effectively product manage all the gnarly research code they produce. It sounds both frustrating and fun.