If a ruined portal within the desert biome is spawned in naturally, rather than spawning on top of sand, it will be buried, usually with a stone slab sticking out from the top.

This has been found after testing many seeds and proving that the vast majority of the time, if you locate a ruined portal either by using the /locate command or a third-party application, it will not on top of land, and buried a few blocks deep at best.

This may also affect Java Edition, although it has gone untested.