What is the difference between using generics and specifying a literal?

Question

typescript

Good evening, there is such a design:

import type { Model, ModelCtor } from 'sequelize';

const isExistsValidator = (model: ModelCtor<Model>, field: string) => { ... }

ModelCtor:

export type ModelCtor<M extends Model> = typeof Model & { new(): M };

But for some reason, if you use a generalization, then the type does not converge:

import type { Model, ModelCtor } from 'sequelize';

const isExistsValidator = <M extends Model>(model: ModelCtor<M>, field: string) => { ... }

Immediately in the body of the function there are errors that I don’t really understand, but that’s not the point.

model - class, descendant of Model
What is the difference between variants with and without generalization?