I suspect you're right about the quantities. In support of that notion, when looking closer at the (linked in another user's comment) PDF of the report, I can see that a lot of this camera's internal structure quite clearly appears to be the product of an FDM 3D printer. This suggests that quantities are low.

And I don't know when that camera was manufactured or designed.

But these days, it's possible to get even hobbyist-quantities of custom PCBs delivered with difficult-to-solder ICs installed from sources like JLCPCB.

(Depending on the features and functions wanted, it doesn't take a whole lot of extra parts to get an MCU to do its thing: There's not a ton of parts on a Teensy to begin with.)

JLCPCB will stick an IMXRT1064 and an oscillator on 5 custom PCBs for you for <$100 - the Teensy is basically $25-$35 for the same thing.