Y'all can argue it all you want, but nobody knows right now, whether Beto's move pays off.
It was a gamble, to be sure. Sydney's thinking is the mainstream. The safe play. Schedule a rebuttal. Hope it gets press coverage, beyond the Tribune and some local tv affiliates. In most situations, Beto's scheduled PC gets little play. So in the coverage vein, this move worked. He is now solidly a part of this discussion.
There's also a real possibility that this school shooting is one too many. At some point that day will come. Is this the shooting that changes minds? The smart money is that it is not, but the smart money often sticks with the aging champion well past his prime.
For a campaign that most, including yours truly, gives little to no chance of winning, it was a fairly smart play. What does Beto have to lose if 18 children dead 5.5 months before an election doesn't move the needle with moderates? If it doesn't, he loses anyway.