Dear Nathan Glassburner,
Greetings!
Thanks for reaching out to this community.
Based on your description, I understand your issue with homePhone Attribute still displaying in MS Teams for some users.
Since Microsoft has specific support channel resource for certain different support scope and attributes, we are belong to Microsoft Forum Community mainly focused on Micrsoft 365 Exchange online only. Therefore, we provide some limited knowledge about some aspects of Exchange Hybrid related scenarios. For your query, we have a dedicated team with special expertise in Azure AD sync/connect related queries, so would you mind to connect and place your query on our dedicated **** Microsoft Entra ID - Microsoft Q&A? You may also add Microsoft Teams tag when writing your question. We believe they will give you accurate and efficient solution for your concern.
Thank you for your precious time and kind understanding. For other concerns, please do not hesitate to add your post in the Microsoft Community Team.
Stay safe and healthy. Have a nice day!