The bug
All of its other subtitles refer to the block by its name so this seems inconsistent. Also the block doesn't really function as a portal either, with only one face visually resembling it. Not sure if intended.
Note: The respawn anchor ambient sound currently cannot occur in the game without commands, see MC-184066.
How to reproduce
/playsound minecraft:block.respawn_anchor.ambient master @a
Hi there!
I can confirm for release 1.16.2.