That is not really correct.
No matter how well your engine runs and is optimized there will be a performance difference.
As far as a low spec computer goes… There are reasons why most developer don’t give away minimum specs early on. Because it’s not a sure thing. If you now buy a computer with your min specs and then realize you will need a bit more… Well that computer is useless. And developing on low spec computers is rather painful if you work in engine. If you have one guy for web development / back end / community stuff that works. But you don’t want to work with lower specs than you have to in any kind of graphics environment.
What I mean is that the stuff in the engine that can change the most due to different hardware is something that Epic has to deal with, not the UE4 subscribers. What the user does is going to be normal type of work, like importing assets, not messing with the code.