strange use of joker in numeric with joker

In numeric with joker there is a joker * that can be used for 'any' number and stones 1 to 9.The strange thing is that the string *123 is legal and 789* is not legal, although in both cases the joker is used outside the range of pool of stones.

(I understand that this caused because in all games 0 is sometimes in the pool and 10 never, but still it is awkward somehow.

I just realized that you mean "j123" and "789j" (where j is the joker).  You probably used a * which the forum interpreted as bolding.