Sadly, this is still the case in Release 1.20.5.
Still exists in 1.20.5-rc2.
Still exist in 1.20.5-rc1.
It seems like we won't be able to remove custom names for 2 versions in a row after having been able to in another way since 1.13. Ouch.
This still exists all the way up to 1.20.5 Prerelease 3.
This is now a crucial problem I think.
Removing CustomName is now outright impossible to do due to MC-267259
Can I get control of this? It needs to be consistently updated if there's any hope of getting it fixed and/or seen by anyone else. EDIT: Affects 1.20.3 and 1.20.4
Tested: Any invalid values would result in the command working as normal, but no effects would happen to the name.
From further testing made in MC-264943 it also happens on Suspicious Gravel, the count size has problems from 24 onwards (haven't tested lower amounts yet), the items are randomly distributed for some reason, I can't tell what kind of distribution this thing follows yet, and it's messing with tables that drops Suspicious Blocks with a count more than said amount, since it always creates this kind of data before dropping the item.
Still exists in 1.20.6-rc1. Is this even a critical bug?