"It doesn’t have to be O2O...even HS crews here use headsets."
Curious statement. Somebody please correct me if I'm wrong, but I believe "O2O" simply means "official to official," and does not reference any specific style of brand of communication equipment. So, crews in Texas using "headsets," are, indeed, using O2O communications.
Yes, there is a significant number of HS crews in Texas using O2O electronic voice communications. But it is not a majority, yet. I'm sure, in time, that will change, and a majority - eventually a vast majority - will be using O2O communications. But not yet.
As others have noted, not even all NCAA crews are using O2O systems, yet. I'm sure that will change, too. Probably sooner than the majority of HS guys in Texas.
Robert