I cannot answer for Alperen, but I commonly encounter this when writing testing code: generally I use the format:
some_module.py
tests/test_some_module.py
where it is expected the filename to test a module is "test_module_name.py". However, within that, I might want to namespace based on the class in some_module.py. If you use something like unittest, classes are natural but if you use pytest it is unnecessary and commonly I end up with what Alperen has: marking everything as classmethod. What I have been looking for is a class/mixin/decorator that marks all methods I add as classmethods.
Why bother marking as class_method? Well, I think it is bad practice where possible to have unused input in functions, even in testing code. Often I have made mistakes for example in copy-pasting and it would be caught if you look at unused variables and such matters.
YMMV, but this, in some form, gets a +1 from me.