I’m a principal software engineer. If it takes me more than a month to get up to speed with an organization (I usually work with small-mid sized companies), I consider that a failure. Six months to first contribution is insane.
First contribution is not the same as up-to-speed. I'll also note that a manager often needs a broader view of the company than an engineer, though at principal level I'd expect the gap to be less (but it isn't always).
First Contribution and Up to full speed ramp up are completely different things.
Expectations at FAANGS is that it might take a month or two for the contribution to start (one week, if you count bootcamp tasks at Meta), but it takes about 6+ months to full ramp up at the Senior+ level.
Regardless of how good you are, you're ramp up time is very dependent on the place.
If you're walking into a place with very little in the way of documentation and process, it could take a while to learn enough to be effective (ex: 50 different microservices and 5 different stacks, nuanced environments, etc.)
On the other hand, if everything is very standardized and well documented, you can jump right in.
If it takes 6+ months just to get "up to speed", are you really having much impact when you leave 6 months later?