Looks like the new forensic report concludes the trigger had to have been pulled in the gun Baldwin was handling. I believe there was some film evidence looked at from the set as well. It doesn't specifically say there were no modifications, but I would assume they were looking for them, as that is a big claim that was made, leading to the charges being dropped against Baldwin (that can be re-assessed) and this whole forensic examination.
https://www.latimes.com/entertainment-arts/business/story/2023-08-15/rust-alec-baldwin-firearms-report-trigger-pulled