Curious about that myself.
It would open up a great question about 'training'. Since Kanan was able to teach her how to use the Dark saber, she clearly showed an aptitude for dueling with a weapon that can be hard to control. If Ahsoka has continued to train her, then she could be fairly proficient.
That would then bring in a question from some as to why Ahsoka would train Sabine but not Grogu. I think that's answered by the fact that Sabine would just be training to use the saber, whereas Grogu was needing to be trained as a full Jedi.
Either way, I'm here for it. REBELS was incredible.