Is this fairly common? Thoughts?
When I started kickboxing I was taught an orthodox stance. Then in my late teens / early 20s I studied Jeet Kune Do (Bruce Lee’s version of Wing Chun) I was taught to stand power hand forward, the concept being to develop a knockout jab.
After a few years of that I started training MMA with standup based on Muay Thai, which was orthodox again. Most recently training the standup aspects BJJ, I am back to a southpaw type stance. It takes a period of adjustment but you can learn both, and learn to switch, and many high level practitioners do exactly that*. Having the versatility to switch stances can be a big advantage.
Saying all that, grappling is infinitely more difficult to learn so if you are worried about their development as martial artists overall, get them started now.
*not saying I am a high level practitioner.