Hostile mobs can spawn on ice, despite it being a transparent block. Tested in the overworld and end, and hostile mobs do spawn (see attached images).

Found a similar issue from 5 years ago (MCPE-25869), however that issued was marked as resolved and "cannot reproduce".

Here is a reddit post from a couple of hours ago, which lead me to test this behavior: reddit.com/r/Minecraft/comments/110lu91/why_are_endermen_spawning_on_ice_a_transparent/