Seems like both are supported. In addition to that, when I deliberately made typo there, the application just won’t start at all.
So seems like these both are fine, since application does indeed start with these, just I do not see theses 17 processes anywhere..
The npgsql project has its own support channels, this question doesn't meet the point of this mailing list nor the PostgreSQL server lists generally, but I was curious and took a look around their documentation (not helpful) and code. I don't see where the driver, upon initial connection with a pool, forces open a number of connections equal to the minimum specified. The minimum behaves such that once exceeded the number of open connections will then not decrease below that number. It doesn't proactively open connections to obtain the minimum - not an unreasonable choice.