More than single digit, but I don't get how this is relevant to the question at hand?

This seems to be about manager-to-manager-interactions, not about manager-to-employer interactions or organizational issues stemming from a particular number of subordinates.

Sure if you are the only person at your department you might be in a different position, as described in the article — but I stand by the statement that calculated optimism is a superior stance to stoic pessimism — again, regardless of the number of subordinates.

Now you could convince me that there are certain particularly cut-throath-on-th-sinking-ship-institutions out there where all you're doing is constant damage control and calculated optimism under these circumstances would be aomething you could neither afford, nor would it change anything. Granted. But I wouldn't choose to work there and if I worked there I wouldn't choose to stay there.

In TFA I wrote that you can remain lucky for a while if you are managing a good team of a double digit size, among some other situations.

Luck runs out much more quickly at triple digits. That said, even at single digits, it's good to know how things work when you're not so lucky.