Most of full stack web devs I know know everything but know it anywhere between poorly and ok-ish. It works more or less fine until there is some issue which requires deep knowledge of either of the stacks.
Generally I'd prefer to have front end dev + backend dev in my team over two full stack devs.
Not only in writing but also in plain English.
I see situations like described below over and over.
Example 1 - too much details.
Morning stand up.
Manager: what's the status of that new feature.
Senior Engineer: well I tried to call that service but it was timing out so I spoke to Bob and he said to check with DBA on why that stored procedure but it's so slow and turns out index is missing so we tried to add it but mysql and varchar something fckn something...
Dude couldn't you just tell it's delayed due to DB and then expand if needed.
Example 2 - insufficient details
I return from the meeting and discover avalanche of emails, chat messages and urgent meeting invite, all with same topic - "Blah service fails, we are blocked" but no details apart from that. On the call I get description of the problem - blah service fails and how everyone is blocked and how infinitely critical it is and what ETA for resolution would be.
What endpoint? How does it fail - timeout, connection aborted, 503 response, 200 response but with error message?
Can confirm this and it was surprise for me when I discovered it. I assumed they would try to maximize $$ in my offer in order to maximize their profit. Yet most of them were trying to get offer accepted as quick as possible. Seems like more offers with less money in each is preferred over less offers with more money in each.