I did send a passport pic, and then about an hour later I got an email confirmation that they were able to verify, so I guess all seems ok.

I think it is better to send a passport pic than a drivers licence for security purposes. If your passport ever gets stolen/used for nefarious purposes, you can cancel it and another will be issued with a new number. However, your drivers licence number never changes, so it is worse for you in terms of identity theft.