Required fields behave differently on Dynamics 365 Forms as that of on the Business Process Flow. Especially when you have ‘Disabled’ them.

On Forms –

Once you have disabled a required field on the Form, the Save action ignores the same and lets you save the record.

For obvious reasons, the required field on the BPF is ignored when you save the record on the form with all required fields filled in.

On BPF –

The required field cannot be ignored to move the Business Process Flow to the next stage!

You’ll discover this soon. Hope this helped. 🙂