My observations identified by URLs #2 and #3 were uploaded with the Android app, each with the same two photographs.
After reading the post identified by URL #1, I checked my observations identified by URLs #2 and #3 and found that, contrary to what that post shows, the photographs in the observations are not deduplicated between, or associated with, both observations.
(please provide a set of steps we can use to replicate the issue, and make as many as you need.)
I guess…
Step 1: Use the Android app to post two observations with the same photograph.
Step 2: On the iNaturalist website, view the metadata of each observation’s photograph.
Step 3: See that the photograph is not linked to both observations.
I hadn’t realized that “duplicate” is a specific function of the software rather than merely uploading the photographs again. I see the “Duplicate” option now.
Automatically deduplicating/linking photographs separately uploaded to multiple observations would be nice, maybe for iNaturalist’s storage costs¹ as well as for users, but that’s more a feature request than a bug report.
(¹ although I don’t know whether iNaturalist’s storage may be doing deduplication already on its own)