It's not a "guess". The last Android release that lacked support for block-device-level encryption was KitKat, which shipped in 2013. Any device being advertised with the "Android" trademark (to be fair: AOSP-based clone OSes like Amazon's have been slower to evolve) over the last two years has that support.

Please don't hijack an important security discussion to engage in meaningless platform flamage. Users with Android phones have this available and they should enable it, not be told that they need to "guess".