How normal is it to be mostly hands-off as a senior engineer?

This is very normal as a senior engineer at a massive tech company like Meta: I remember back at Instagram Ads, I was given feedback to write less code. Like many other mature orgs in the company, Instagram Ads got to a state where the biggest value add wasn't writing code anymore: It was aligning people and being more deliberate about planning and product direction. There were many E5s and E6s in my org who had less than 25 diffs a half and were doing fine.

At the end of the day, the expectations of an E5, especially one operating under the tech lead archetype, is to fill in the gaps and deliver the project well, doing whatever it takes. It seems like you're doing a great job here as there are many non-technical gaps in your workstreams that your more junior teammates are less well-equipped to solve and you are filling them.

All that being said, diff count is super important and is a metric that is always looked at in calibrations. I would make sure that you stay in-sync with your manager about expectations here: Maybe there actually is a "red flag" diff count number they have in mind that you shouldn't dip below.

For a bunch more thoughts around aligning with your manager about performance expectations, check out our 1 hour deep-dive on performance review.