One of the fundamental differences between CPython and Jython is that the latter is fully and truly multi-threaded. Jython has no GIL.
That import always takes a lock doesn't create additional lock contention in CPython because the contention is on CPython's GIL.
Ignition performs auto-importing of project library scripts on first use after a project start or restart (edits). That auto-import is lockless, for huge performance wins under busy event load. (But just the fast path is lockless in v8.3, fixing a longstanding bug.)
This is a huge performance win in Ignition because many, many events firing at high rates will crush that interpreter-wide import lock.