This Special run is currently in progress! Maybe in May we will have thes etubes if Corona did not stopped everything.
Regarding making 18350 tubes per default, if I remenber correctly Hogo sttated it is not fun at all to assemble thes tubes. This 18500 and 18350 tubes were only available as accessory not available with any light Option.
I guess the walls would be a lot thinner making the signal wire harder to machine just right.