While Sprint & Clear share the infrastructure they are not the same company and do not have the same policies.
When I was on Sprint back in the Fixed Wireless Internet days they did not throttle then either but you were impacted by the number of users on at one time.
If there is throttling now it is not such that it impacts "normal" use (gaming, streaming, browsing, etc).
My connection is shared throughout the house and I have not checked but the drop in speeds could be due to what else is happening.
Suffice it to say that even when I am "throttled"; my speed is at least 3Mbits down.