From reading the documentation, it would seem that FB messenger webhooks only work on business pages - to generate leads, reply to questions, etc. The docs imply (but do not state explicitly) that this webhook only works for business pages and not personal pages.

However, obviously many services and apps exist that allow users to message others using FB messenger (e.g. Beeper, Matrix) or do something on receiving a facebook message (e.g. ITTT, Zapier).

So do they use the FB/Meta pages messages webhook, or some other API?