Type inference (not just Hindley-Milner) is divided in two logical phases:
(0) Generating a system of type equations, by recursively scanning the AST.
(1) Solving the system of equations. The nontrivial nature of this step is what makes type inference, well, inference.
In Go and C++'s case, the generated type equations come out already solved (that is, of the form `TypeVar = TypeExpr`), so there's nothing to infer!
Perhaps the parent was trying to talk about "HM type inference" or something, but "type deduction" is also a fine name for a subset of type-inference, and perhaps more explicit for C++ and Go.