No it’s not required. My 24 month contract was almost up so paid off the two months I had left and had it unlocked just to do some testing on a few other carriers with the esim. Atm my esim has T-Mobile Prepaid. And getting about the same download speeds of between 100-130 mbps on both Sprint and T-Mobile. Uploads are usually around 5mbps on Sprint and about 9-12 on the prepaid T-Mobile line.
Sprint LTE Speed Test
T-Mobile Speed Test