There is no special death message for falling onto a bed
Relates to MC-277709 and MC-277710.
The bug
If something dies of fall damage on a bed, no special death message is produced, despite it being a block that modifies fall damage.
Since pointed dripstone, another block that modifies fall damage, does have its own death message, it may be expected for beds to also have such a message. See also MC-173484, MC-173485 and MC-219892.
How to fix
Make this use its own death message instead of the generic message.