All blame must go to Android. I retested in an iPhone using Firefox, chrome, edge.
All 3 show ad blocking when on mobile data.
Using the same browsers on Android, there is no ad blocking when on mobile data.
hmm not sure if that should be such a generic statement. I’m using Android devices only, and for me ads getting blocked. Doesn’t matter which browser I’m using. Just tested again on a Pixel4, which is a pure Google mobile device.
Maybe it depends on Android version, browser app version and/or other apps installed. At least in Chrome you could aktive some lightweight mode, where google is trying to speed up web sites and to save data volume. Probably there are other app trying similar. Who knows. 