I'm the developer of PINN, a fork of NOOBS for the Raspberry Pi.
I've noticed that the partition label names for LibreELEC in LibreELEC.tv/partitions.json at master · LibreELEC/LibreELEC.tv · GitHub are too long to be used as partition/volume labels. They currently have names like "LibreELEC_RPi2_System" and "LibreELEC_RPi2_Storage" derived from your distroname and project name.
However, FAT partitions have a maximum label name of 11 characters, and 16 for ext partitions.
NOOBS may also add a single digit to the label name to make it unique if necessary, further restricting the original name length to 10/15 characters.
In addition, NOOBS will ignore any partition label >15 characters. This is what is happening in the case of LibreELEC and its partitions are not being labelled at all.
This seems a bit of a bug in NOOBS, but the developers have indicated they are not planning any changes to NOOBS in the near future.
So I suggest the partition labels used for LibreELEC are shortened to 10 characters so that their partitions are labelled correctly.
I shall try to put a fix in PINN to workaround such issues, but even so it is not clear how to do this universally. For example, If the existing label names are truncated to 10 characters, both LibreELEC partitions will be given the same name before the single digit suffix is added to disambiguate them. Maybe LE2System and LE2Storage would be appropriate? But I'll leave it to you as it seems to revolve around some macro system. Whatever you choose, please ensure consistency with their associated tar files.
In NOOBS, this is largely a cosmetic issue, but it makes identifying the partitions much easier if they have the correct names.
In PINN it is blocking a new feature, so I will have to work around it somehow, but I'm sure it would be better if the partitions could be labelled consistently in the first place.