We could enable support for automatically detecting DoH support early but it would be risky. We're planning on following along with Android's schedule for enabling these and nearly all other features. DoT does usually work perfectly fine.
Android's DoH implementation is newer than DoT so they wrote it with fancy async Rust. Rust has become the preferred language for new low-level code in Android. DoT would have been Rust if it was added today. DoT/DoQ are just losing to DoH due to the port.