Us Aussies apparently love the TG shoulder mount! I learnt the twisted grip hand position from my very first level, and did little "hitch kicks" in it, then slid that down to the floor. It was only after about a year and a half that I learned to shoulder mount into it, and by then the hand positioning was so natural to me, and I understood the amount of pull I needed my muscles to have for it to be safe.
When I was 15 I dislocated my shoulder and tore my rotator cuff. I could not move my arm any higher than parallel to the floor for about 2 years, with lots of rehab and physio in between. So ,because of that old injury I still have quite a lot of tightness in my shoulder muscles. and even I don't find it difficult, or likely that I will injure myself.
That being said, I have had a lot of practice building up to it, with my arms in the position. So I think it would be very different for someone not used to twisted grip to start off learning to handspring or shoulder mount with that grip. You have to learn to crawl before you can walk, and walk before you can run.