Ok, I did some investigation and it looks good!
* it does not store label in upper case
* dosfstools since 3.0.16 disallow setting new label if is not upper case
* dosfstools since 3.0.22 allow setting new label in lower case, but throw warning
* it reads label from boot sector instead from FAT root directory
* dosfstools since 3.0.16 read label from FAT directory, with fallback to boot sector
Plus since since 3.0.16 dosfslabel and mkdosfs creates entry in FAT directory if does not exists before storing them label. So label is always stored to both FAT directory and boot sector.
So if gparted detects existance of dosfslabel (resp. fatlabel) with version 3.0.16+ then it can be used for getting or setting FAT label. Still gparted need to correctly prepare label (in upper case).
https://github.com/dosfstools/dosfstool … 6519860cb4
So... is there still any problem why gparted cannot use dosfslabel (resp. renamed fatlabel)?