Hello Lucin ;
I encounter like these traumatic nerve injuries around the shoulder and scapulothoracic region . I had seem something like your patient and a supraspinatus nerve injury .

The Point of specifity nerve injury could occur in case of comperssion aetiologies , but I think in case of traction/stretching injuries no rule specific e.g. in Erb's palsy .
The progress / outcome according to the degree of nerve injury ,but I like to raise point PAIN around shoulder could disable the patient from abduction to the degree the practionner imagine it is nerve / paralysis .

cheers
Emad