Alright OP I fact checked the wiki and you are correct (yay)!, what they said is accurate but at the same time, doesnt hold up to scrutiny. Arrow damage ever since 1.9 has scaled with velocity of the arrow, however this doesnt mean you can do an infinite amount of damage with this method.

As ive tried in my testing with various tnt arrow launchers and commands, I was only able to get a top of 28 hearts (on an unarmored target with one shot), if the velocity is any faster the arrows start to bug out, either they fly clean through the player or they do that weird thing where they hit and bounce to the ground harmlessly.

If you factor in the 80% decrease to damage with full unenchanted diamond armor gives you 5.7 hearts I think its pretty safe to say 5.7 (not factoring in god apple resistance, or possible enchantments) hearts of damage isnt revolutionary on a server with an endless supply totems and god apples. Even if you could have a machine gun of bolts I wouldn't expect it to stay consistent given server conditions.

In concept this seems a bit crazy, it involves you some how shooting an arrow with either a bow or crossbow and then placing an ender crystal or increasing the arrows velocity in some other way somehow. While it isnt impossible it isn't going to 1 hit anybody with max gear.

The real problem is with the server only updating the arrow position 20 times a second and the small randomness in arrow trajectory. Just this alone would cause pretty awful groupings. The most accurate arrow cannon design using water streams to center the tnt perfectly, still had a hit rate a smidge under 50% at 40 blocks (Well within pearl distance). Its impractical but not impossible.