1.) Their endo/doctor told them to inject that way for a reason. They’re not going to tell them to inject subq for fun.
2.) Some doctors are switching and having their patients do subcutaneous injections because it releases the testosterone more slowly due to the lack of blood supply in subcutaneous tissue. This not only prolongs the T being in your system, but also is beneficial to people just starting T because it more slowly introduces it to your body.
I got this information from my endocrinologist & her nurse and have confirmed it through my own research. However if you know better than they do, please feel free to correct what I have learned.