Until flashlight apps stop trying to request location data, I do not feel it's safe to assume the industry has no data
And there were like 2 ads shown to you during this 50 seconds period, while you were in the dark and not looking at your phone but using it as a duh, flashlight. And then you stopped the app to save your battery.
Do you really think some advertiser benefited by using this data?
And what "independent" ad-tech is dealing with is millions of cases above. Consistency is important. FB and GOOG have consistent data, collected over days and years, properly matched, correctly aggregated. All others are dealing with flashlight crap.
A lot of those arguing your parent comment's point in other threads here and elsewhere seem to magically forget background data. Out of sight, out of mind.
Use a simple app to track background connections on your phone (e.g. NetGuard or the like) and you'd be amazed at how much gets sent back to the mothership.
Mobile apps are 1000x more invasive than anything on the web and these SDKs constantly send data in the background. There are also 100s of signals that get correlated to build single device profiles across time. FB/GOOG do have an advantage but that doesn't mean everyone else is useless and if you have ISP partnerships then you can actually get even more consistent data down to a device and household.