You would be wrong in expecting that, the Tesla uses its center as a crumple zone if the sides are too stiff in the NHTSA test the car will stop too fast leading to injuries in the crash test dummies and a poor rating. Because of this it is fair to assume that the sides are not as strong as another 5 star crash test recipient with a front combustion engine. If there is only a partial impact the combustion engine still has half its crumple zone while the Tesla will have 25%.
You are assuming that the Tesla and other cars both start with the same "amount" of crumple zone. But if the Tesla actually has twice the amount of crumple zone, then having 25% of it left would be exactly the same as 50% of the normal car's. Taking the engine out gives the Tesla extra margin, it doesn't just move the same amount of margin around.