I did see a few studies about muscle shrinking in general when I looked for this one. They all were fairly small, though and not that long ago. Hopefully scientists are developing/working on larger, more conclusive studies. But those take time, unfortunately.

One study of 106 people found that muscle loss stabilized after 12 months, but it was very clear how small the study was and which participants dropped out because they had to go off the drugs.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12673431/

Scientists seem to be avoiding making strong statements about this for usual scientist reasons - they want to see larger better studies. As a layperson, however, I'm definitely keeping it in the back of my mind and if a doctor recs the drug years from now, I'll be looking up what conclusion they came to.