Moving at low tick rates is slow, yet moving at high tick rates isn't fast

When moving at a very low tick rate (e.g. 1), the player also moves very, very slow. However, when moving at a very high tick rate (e.g. 5000), the player moves at normal speed.

How to reproduce:
Set tick rate to 1 and try moving. Then set tick rate to 5000 and try moving.

Expected and Observed results:
On the first attempt, the player moves extremely slow. On the second, the player moves at normal speed, despite high tick rates.