So I've looked around a bit and apparently it was confirmed on Oha Suta, in the same episode that confirmed the Pallet trainers to be Tierno and Orange Islands Marina (and this was conclusively proven, as they showed a picture of the original Tierno and Marina alongside the Pallet Trainers). Apparently it was only mentioned on this Oha Suta episode, if we have to believe the user who added it to Bulbapedia and several users on Serebiiforums (including Dephender, who I'm pretty sure we can trust).