Please post the links to your information, especially any updates that bear on the Ellenbecker video.
There is another mode discussed for shoulder injury. I viewed this video more carefully after your brief comment in another thread.
One injury occurs on the bursa/acromion side of the tendon - sub-acromial impingement
, see 1.00 - and the other injury occurs on the articular cartilage side of the tendon, see 39 seconds, as described in the video. See video for details, illustrations and definitions.
I am very uncertain since looking at that video and don't know the percentages of shoulder injuries or the circumstances for each type injury. If you have more recent information on percentages, please post your updated sources. This is a subject that needs creditable publications for information.
In any case-
1) ATP servers are mostly seen to use the shoulder orientation limitation as recommended by Ellenbecker. There are some more details that have been discussed in detail on the forum. Look at high speed ATP videos for examples of good practice. There are exceptions, and even Federer seems to show a high upper arm. Look at a number of ATP servers. Look at their shoulder-upper arm orientations
over the service motion. Don't translate it into words. The better information is in the frames of videos.
2) The details of how shoulder injuries occur have been speculative. If details have been updated from the Ellenbecker video, let's post the sources of that information.