[mti]

While not mentioned by the author, there is an alternate reason why finite field DH can be seen as a special case of ECDH, kind of: namely, there exists special elliptic curves (actual, smooth projective curves) that do have an efficiently computable endomorphism to a suitable form of the multiplicative group, via pairings. This is in essence the MOV attack against the XTR cryptosystem. That doesn't fit neatly in OP's framework, though, because the map isn't a morphism of algebraic groups (it is efficient for other reasons), and it is cheating a little bit, because the inverse map isn't efficiently computable.

Another point that the author glosses over a bit is that higher dimensional abelian varieties offer other instances of DH that are genuinely different from ECDH, and that are occasionally useful (mostly the case of Jacobians of hyperelliptic curves of genus 2). There isn't really a trick to make an arbitrary hyperelliptic curve DH/abelian variety DH instance a special case of ECDH: if anything, the relationship would be in the reverse direction.