Agreed. Surrounding well armed pit bulls can draw down on your forces needed elsewhere. Possibly even a trap.
But these pit bulls ain’t chewing up the neighbors kid while they are being held at bay.
And...you can just sit back, keep them at bay. Sooner or later they are going to get thirsty.
The larger concern is what happens when you surround a large Russian Army? This is the time when an unstable, frustrated, and demoralized leader decides that “he will show us” how tough he is.
I doubt the Russians intended to be surrounded.