This is now fixed with v2.31 of the MusicBrainz expanded WSS.
As in most other fields with multiple values, I have used the slash / as separator.
Feel free to replace this separator character with one that you prefer.
Just change Line #708 in the new v2.31 file MusicBrainz expanded.inc from
say "/"
to - for example
say ";"
to directly get GB;GB;GB instead of GB/GB/GB from the new v2.31 WebSourceScript.
This allows you to skip the above regular expression and additional Action.