I never said reductionism is a one way street.

But in simulations you usually work bottom-up (in abstractions). Of course, sometimes you can't do that, because it's overly complex.

My field (electrical engineering) has a lot of physics as well and I don't mind if those who invented the techniques I use were physicists or engineers (or something else), or if such and such things are in the "engineering" domain or the "physics" domain, I just use them. The point is moot.