I had a look at the account in question, and I think I found what the issue is - the user was flagged as a spammer on Oct 17, and although the flag was resolved and the account unsuspended the very next day, the observations have not properly re-indexed.
Although it has over 8k observations only 800 turn up in “identify” mode with the broadest search parameters… until I add “&spam=any” to the string, then they all appear.
I myself had the same issue a few years ago, here is my post:
https://forum.inaturalist.org/t/observations-still-marked-as-spam-after-resolved-spam-flag-on-account/28754/14
And here is the github bug report:
https://github.com/inaturalist/inaturalist/issues/3348