JQL search documentation specifies that the tilde is an unsupported operator for the fixVersion field:

https://support.atlassian.com/jira-software-cloud/docs/jql-fields/#Fix-version

 
Despite this, the symbol appears in the operator-dropdown for the fixVersion field when typing in the search input for a JQL query:

Expected behaviour

Search operators should only appear in the dropdown if they are supported for a given field. This is how other fields behave e.g. for issuekey (where the ~ operator is similarly unsupported) the unsupported symbol does not appear in the operator dropdown: