I think that theory is flawed because it's based on assumptions.
Real data disproves it handily. For example, people shooting 7.62 NATO Garands saw no accuracy degradation as the bore and groove diameters enlarged .002" from bare steel cleaning rods rubbing away metal at the muzzle. There was copper wash all the way to the crown when new. After 3000 rounds, accuracy was still the same but the copper wash stopped near 3/4" back from the muzzle. Muzzle wear gauges showed a .002" increase in bore and groove diameters. Ten times as much as Chris Long's numbers for muzzle enlargement from shock waves.
Too many people have shot the same load in different barrel lengths with the same good accuracy in each.
I think that OBT stuff is one of the myths that most people cannot see the flaws in. One is a rifle barrel's resonant frequency is typically less than 100 Hz. So says mechanical engineers using the fourth order equations getting good answers. Check out www.varmintal.com the Barrel Harmonic Movie. And his speed of sound in barrel steel is incorrect. Plus, sound waves don't stop at the receiver; they go back to its tang then bounce forward.
I've put an accurate load in all sorts of barrels with one shot. Never worked up any load for different barrel lengths for the same cartridge. Nobody's got better accuracy.
Nobody's proved that OBT theory is correct measuring bullet exit versus pressure pulse position.
As bullets with a wide range of weights and muzzle velocities won't have the same muzzle velocities and barrel times for a given load in the same rifle shot by different people. There's easily a 100 fps spread for average fps numbers. Yet the same load shoots equally accurate across several people. If Long's OBT really worked as claimed, a different load would be needed for each of several people shooting the same rifle.
The one nice thing about advice is that you can always ignore it, and or take the bits that apply to your theory...
Nodes and resonant frequencies mean little to guys like me who have a hard enough time simply maintaining consistency from one round to the next. 1/10th moa from resonant frequency modulation is not going to trump 3/4 moa spread from varying neck tension when I'm seated into the lands. For guys like me who simply trying to maintain a decent consistency the best strategy seems to be eliminating or at least moderating the variables that introduce that inconsistency. Finding a propellant/primer combination that starts with enough pressure for the bullet to deform properly and then adjusting the charge just enough to eliminate muzzle upset is something I can understand. I've been accused of "overthinking" but WOW now I'm losing sleep over resonant frequencies