Jira REST API get labels returns empty label (label that is not used at all)

I am using JIRA Cloud Rest API to fetch labels (both v2 and v3) https://developer.atlassian.com/cloud/jira/platform/rest/v3/#api-rest-api-3-label-get

It sometimes returns labels that do not exist i.e labels that are not tagged by any issue. The way labels work in Jira, these labels should not exist in the first place.

If you go to issue view and try to use these labels, they in fact do not exist. So looks like Jira is using different API internally.

Did anyone face this problem?