Hi, and welcome to the forum!
On the next run, restic will descend into the bindmount and read and hash all files in there. In the process, it’ll detect that all data has already been uploaded to the repo, so it’ll decide that there’s no need to upload anything. In the resulting snapshot, you’ll have the pictures in two locations (/media/HDD1/Pictures and /home/MelcomX/Pictures).
Restic does deduplication on blobs, per repository. A blob is usually only saved once in a repository.
I hope this answers your questions!