The primary effect of amphetamines (that matters) is VMAT inhibition. While lots of drugs hit lots of receptors, and there are lots of overlap because of this, this does not make different compounds equivalent.

For example, off the top of my head, mescaline is also in the phenylethylamine family but is a wildly different drug with different receptor bonding affinity and subjective effects. I doubt anyone would want to mix up the two.