PPROVIDER_EXCEL requires initialize_excel in all classes

[tingeman]

The new PPROVIDER_EXCEL requires an initialize_excel method to be present in all classes in order to be compatible.

What is the intention behind requiring this dependency?

It breaks the design philosophy that the core model classes should be unaware how parameters are obtained.
When a new PROVIDER class is implemented, all other classes in the model will have to be modified with a new initialize_newprovider method, if we are to follow the PPROVIDER_EXCEL implementation.

What is the use case scenario, where a particular class needs to know if the data came from an Excel or a Yaml file or something else?

Could we change it to just a generic initialize method, without loss of functionality, and thus avoid touching all classes when a new provider class is implemented?