like a demand or a supply elasticity
This is actually my main gripe with the way they talk. Estimating elasticities is absolutely part of economics proper and they acknowledge that. It's easy to miss that, though, when reading pieces like this, even though the author never actually says anything to the contrary.
like how engineering is considered separate from physics?
There are a couple of interesting parallels to that.
  1. Finance, even if rooted in Austrian theory, is usually considered a separate discipline from economics.
  2. While still being considered part of economics, Austrians have an interesting perspective that empirical work is best understood as doing economic history.