I struggle with the same pattern and worries myself, though mostly internally. My position affords a lot of latitude for it (I replaced the previous lead dev 10 years ago when the company was 5 people). It seems to be (and is said to be) okay with others as long as I communicate even as little as, "I'm deep in the weeds on this and probably will be for the next 2-3 weeks."
I worry about the optics of it, but at least have confidence that other developers can see the end result is solid for the total amount of time invested. Smooth workflow for everyone is the other major concern, but again we're lucky to be working on our own system and not beholden to external deadlines.. and I guess lucky to have enough want-to-dos in the backlog that no one is ever without something useful to work on.
We do create a bit of expectation of every developer having at least some tasks each week that are picked up and some that are completed, and it's tempting to just game that a bit to put up some numbers on the weeks where I'm figuring out how to do what I'm about to do.