Hi Sandi Andersen,
Thanks for reaching out to Microsoft!
You're correct that the search/query endpoint will not provide the top search terms for SharePoint, as there is currently no capability to achieve the same results as the M365 Admin Center's Search & Intelligence - Query Analytics via API.
Since this feature/functionality is presently not available, you can submit a feature request idea using support link, which will be monitored by Microsoft team and make the enhancements to Microsoft Graph APIs. I will also upvote for you.
Hope this helps.
If the answer is helpful, please click Accept Answer and kindly upvote. If you have any further questions about this answer, please click Comment.