Somewhat related discussion: Default Editor settings instead of persistent
The current behavior is weird, agreed. Switching to a note of the same notetype should keep the current state. But switching to a different notetype, the field probably has a completely different job, so it should reset to a default (or the setting of the last note of that notetype).
Maybe we could remove the setting from the fields dialog. But I don’t know how feasible a per-notetype entry in the profile manager would be.