Wow, sounds great, I want to test it again!
I tried the app early this year, I don’t remember when, probably before most enhancements.
I remember it still did not help [me] in not buying duplicates while shopping, quoting @sbontrager’s comment from the current most voted MOBILE ticket, herebelow, for the record. 
To be fair enough, MBS itself does not allow me this either, except if I use musicbrainz.org through the following Android funny stuff:
-
ZXing barcode scanner with a specific custom search URL:
https://musicbrainz.org/search?type=release&method=advanced&query=barcode%3A%s - Kiwi Browser or old Firefox 68.11.0
- Violentmonkey extension for Kiwi or add-on for Firefox
- mb. REDIRECT WHEN UNIQUE RESULT
- mb. COLLECTION HIGHLIGHTER
Which is already super good but requires quite some setup, a regular maintenance and is not well known.