Maxis FUP T&C still state they have a right to throttle your streaming speed once your principal and share line(s) exceed 300GB in a calendar month. It means they may or not may throttle your speed.

My parents have been using Maxis Postpaid 98 Unlimited since the MaxisONE days and their mobile data was never throttled. So i guess it only happens if they find excessive use of mobile data for your account.