Js this and callbacks - React 18: Intermediate Topics

Hi All,
In video 20- Creating a Reusable API Client, Mosh goes over the following line in useTodos.ts when there is the white screen error

queryFn: apiClient.getAll,

He says there is an issue with this (from the getAll method in apiClient.ts), that this loses it’s context and becomes undefined, like it is a stand-alone function, not a function that is part of an object. Fixes are to use bind() or to convert the getAll regular function to an arrow function.

I am wondering why there is this issue with this in the first place, because it is a callback?

Any links or explanations of why this is the case are appreciated. thanks

found an explanation here, so class methods as callbacks are not bound by default