That’s moving at faster values though, so no, a Zealot at that speed would move 28.57% slower than unstimmed Bio when it is hit by concussive shells. This is not enough to catch up to fleeing Bio even without stimpacks.
By contrast, if you meant 4.5 speed in normal/editor values, then Zealots would move at the same speed as unstimmed bio (2.25) when hit by concussive shells, but they still would not be able to keep up with stimmed bio.
The fact is that as long as concussive shells exist, Charge is necessary or Zealots will never get a hit on fleeing stimmed Bio.