Why is cryptographic model not considered formal methods?
Disclaimer: I'm currently doing a PhD in Formal Methods and Cryptography and I'm not really sure of my answer.

The first application of Formal Methods is to be applied to pieces of software. The goal is to prove security properties on them. These are usually safety critical softwares (those you find in planes, trains, nuclear facilities...) This field is called Software Verification.

I mostly consider Formal Method as a way of arguing, a way of thinking or proving. In this case, Formal means without ambiguity. Thus you could consider any approach with such mindset in the domain of Formal Methods.

To answer your question, [from my point of view,] both approaches qualify as in the Formal Methods (and I don't see why they should not).

E.g. Easycrypt, a tool to make proofs in game based model and probabilistic models is based on Why3. And I'm pretty sure that Why3 is part of the Formal Methods approach using theorems provers and SMT solvers such as Alt-Ergo or Z3.