[Need Confirmation] Please confirm Azure Function App can't not scale over 20 instances when in private endpoint

Hi team, I have struggle with issue of HTTP Trigger function can't scale over 20 instances.
When I log a support ticket to Microsoft support, they advise me that because my function app is in private endpoint, so it can't scale over 20 instances.
However, I can't find this behavior mentioned anywhere in official documents, so I need confirmation from the team. Please let me know if it's a design issue.
If it's true, it would be better if the team share some insights, or any plan to fix it.
Thank you.