Yes, I have had similar experiences, sometimes even fewer are recorded in Matomo (20%).
I see the following reasons:
Facebook counts clicks, while Matomo measures visitors.
While visitors to Facebook have no problem with privacy, they then refuse all cookies on my website.
Since the majority of Facebook users use smartphones, the Facebook app and the Facebook in-app browser, the design of the cookie banner seems to be very important.
The Facebook InApp Browser doesn’t send a “do not track” though, so I don’t think it has any impact on a Facebook campaign.
However, we will now track with Matomo without opt-in, but then without cookies. We will see.