I, too, remember the young man in question. He was a key player in WO-S' trek to the state championship game in 2014 and transferred to the school in the Cy-Fair ISD for his senior year.
I also recall that Coach Thompson indicated on the young man's PAPF form that he was moving for athletic reasons based upon conversations with the young man's father that the move was to "increase college exposure." I also recall that Coach Thompson was heavily castigated on social media (including a lengthy thread here) for doing so as he was accused of only doing so because he was "bitter" and "jealous" and "wanted to punish the young man" for deciding to transfer from WO-S.
The UIL does have in place rules to stem the tide. However, those rules only take effect when coaches from these schools that are being poached do indicate like Coach Thompson did and DEC's give them the weight that the UIL says they should. However, coaches see how folks like Coach Thompson were treated and figure it is not worth the trouble that they will bring for themselves (dragged through mud on social media, travel to Austin to testify in the kid's appeal, etc) OR they have the mentality of "If you really don't want to be here, I really don't want you here" and rubber stamp the PAPF form even if there is evidence of a move for athletic purposes.
Absent either tougher adherence to those rules in place or the UIL coming down with an across the board one year ban for varsity play.....which probably everybody here would agree is too draconian of a measure to put in place...this trend will only increase in frequency.