they will show you their own ads through operating system notifications, but without collecting your personal data to do so.
the program is also entirely opt-in and is thus disabled by default, so the user has to knowingly and willingly enable it.
Meaning the ads will be significantly lower quality. I doubt they have anywhere near as good performance as regular ads, meaning they'll likely have sketchier ads that are willing to pay more to reach a less specific audience.
They also "pay" an absolute pittance if you have them enabled — something like 2 cents per ad, if I remember my calculations correctly. Literally nobody should be considering that trade worth it.