My little finger and ring finger do not move independently. I have heard that the problem is a hand design defect by having the two fingers connected by the superficial ulnar nerve. This defect greatly affects my playing. I have designed many exercises to work on this and have been religiously working on their movement and strength for over 10 years. I have accomplished probably 30% better usage but I want more. If there are no exercises or therapy is there medical or surgical help.
I'm a keyboard player not a guitarist, but the same issue of finger independence is relevant.
I'm not sure your statement is an accurate description of cause, at least for a normal hand anatomy. AFAIK the limitation is the arrangement of the tendons in the hand, not the nerves.
For what it's worth, if my hand is in a relaxed position with all the finger tips resting on a table, I can move my little finger on its own (i.e. lift it, or move it sideways) with as much speed and strength as the first and second fingers, while keeping the other three fingers touching the table. What I can't do is move the ring finger as easily or as quickly, without moving the other fingers. When I try, the third and fourth fingers "want" to move together more than the fourth and fifth.
If your situation is different from that, it may be worth getting some professional medical advice if you don't trust what your guitar teacher tells you, or if you don't have a teacher. I've no reason to believe my hands are "not normal", and I've never done any "special" exercises for finger mobility, beyond a few decades of regular keyboard playing at a fairly advanced level.
I would be cautious about trying any special exercises for this without some reputable advice (i.e. not "a video by some guy on the internet.") It's too easy to cause irreparable damage to your hands that way.