Thank you for posting your query on Microsoft, I was able to get this checked internally
We do have OBO flow for Microsoft Entra External ID on roadmap that doesn't exist in Azure AD B2C. However, we are yet to get anytime line for the same.
Kindly be follow on What's new Entra External ID as all new feature updates would be posted here.
Thanks,
Akshay Kaushik
Please "Accept the answer (Yes)" and "share your feedback ". This will help us and others in the community as well.