The BATFE is pretty stupid technically.
I’d guess that there are 22LR rounds that are quite killer.
No need to guess, there are .22 rounds that are amazingly lethal. In fact I have read one study that was made of shooting records and the conclusion reached was that your chance of dying from a .22LR round was about the same as the chance of dying from a .44magnum round if you fail to receive immediate medical help. The .22 was rated deadlier than a .38 special which used to be the standard law enforcement pistol round. Of course you generally die more quickly if shot with a .44magnum but that just means your suffering ends a little sooner. The real difference is STOPPING power which is much higher with the .44mag. Some people don’t understand the penetration of a .22LR, it can go very deep.
Russian special forces use a .22, the SV99, for sniping.
An older Soviet model was used with a plastic bottle silencer in the Balkans war.