There's nothing specific to read about it, just plenty of anecdotal evidence. People use connection pools because connecting to _remote_ databases is slow. SQLite _is not remote_. It's _in-process_ and _fast_. Any connection-pool _adds_ to the amount of work needed to get an SQLite instance going.

It's _conceivable_ that pooling _might_ speed it up _just a tad_ for databases with _very large schemas_ because parsing the schema (which is not done at open-time, but when the schema is first needed) can be "slow" (maybe even several whole milliseconds!).