Yes, there are a good number of topics about this and similar situations on the forum. Some examples:
https://forum.inaturalist.org/t/is-it-acceptable-to-create-a-second-account-for-things-that-i-did-not-observe-myself/5558/4
https://forum.inaturalist.org/t/can-i-upload-pictures-for-a-friend-with-credit/32237/4
The short version is: The you can do this occasionally while taking precautions mentioned above (saying you are using photo with permission, etc.) but shouldn’t make a habit of it. The photos will be uploaded with the copyright attributed to the observer, so you need to make sure that the person who took the photo is ok with that.
If multiple people were present for an observation, it is fine to have an observation on each person’s account. If there isn’t some type of note in the observations though (like mentioned above), other users might flag it as a copyright violation if they see duplicate photos.