Anyway, There are more paid tracking SDKs in the wild and probably more invasive than Facebook's.
For example, in Poland there is a service called Cluify which supposedly tracks millions of phones to then target ads at them. Although they're Google ads. In fact, they're a "proud partner of Google."
On the website https://cluify.com/ they mention using wifi but in sales pitches they boast inclusion in many popular apps. As their client you can geofence an area and buy ads directed at devices which frequent them.
I purged and fumigated most of these parasites from my phone. Going even as far as replacing the OS because LG thought the Facebook app should be an integral part of their distribution and not removable. Hopefully they at least charged Facebook dearly for it.