Attempting to remove the beam_target tag from an End Crystal returns "Modified entity data of End Crystal" but does not in fact remove the tag. (prior to 24w06a, removing BeamTarget instead reset its X, Y, and Z values to 0, but likewise did not remove the data).

Steps to reproduce:

1. /summon end_crystal ~ ~ ~
2. /data merge entity @e[type=end_crystal,limit=1,sort=nearest] {beam_target:[I; 100, 100, 100]}
3. /data remove entity @e[type=end_crystal,limit=1,sort=nearest] beam_target
4. /data get entity @e[type=end_crystal,limit=1,sort=nearest]

Notice the beam still exists, and the NBT still shows the beam_target unchanged, despite the command returning successful. Other methods to remove the data, such as /data merge, likewise have no effect.

The only way currently to "remove" the beam_target tag is to delete the entity altogether and re-summon an identical one in its place, sans target data, which is not ideal as this causes a noticeable jump in animation when the entity is replaced.