What's standard is standard and there's no real reason for it to be, like Hornady basing their handgun ammo velocity off an 8 inch barrel knowing full well most people are using 3 and 4 inch barrels.
Honestly, velocity is irrelevant to me in terms of barrel length for a .22 that's meant for target shooting, it's accuracy and all my experience has been that the longer the barrel, the larger the groups.
I mean, maybe an Anschutz can shoot better than my Charger, but how much better? 1/4 MOA better? For $1000 more I don't see that as worth it, not unless I was using the gun for matches once or twice a month... which I'm not.
The ammunition manufactures have industry standards, thats just how it is.
Barrel length gets tricky,
Several factors come into play on barrel length.
When shooting Iron sights the longer the sight radius the more potential the accuracy. So the barrels tend to be longer for shooting accurately with iron/match sights.
Barrel length dictates combustion of the powder charge.
Slow powders in short barrels is not good
Fast powders in barrels that are to long is not good.
Some cartridges to get the velocity needed to take advantage of the BC need that velocity.
Now with scopes barrel length only needs to be long enough to get the nest complete combustion out of your cartridge.
Its all fun and the game is to find what works for you.
theres alot of personal likes and dislike on every aspect of shooting
I personally cant see spending $500 plus on 10/22 competition model and putting bulk shit ammo through it.
CCI SV and Aguila extra is about as cheap as I will go in my 10/22 with Kidd barrel. I run the bulk shit in my $100 Ted Williams and other “department store” branded cheap 22s.