It also depends on the depth of "field repairs" you want to do supporting different brands of 1911-style pistols, too. Some of the models made by some of the different big names might have some requirements specific to their products.
Being trained and certified by one of the major gun companies can be helpful in that the recommended repairs and maintenance might be more easily explained (and defended, if need be), in some subsequent court proceeding if your maintenance, repair and corrective actions are later called into question.
Naturally, the different variations and differences might require you defer to a factory repair tech at some point, or whatever professional gunsmithing service is authorized by your agency. (Like dealing with an external extractor or firing pin safety mechanism you might not have been trained to service in a particular class.)
It depends how far your agency permits you to go regarding their exposure to liability, as well as how far you're willing to go when working on some specific make/model.
There's been a number of instances where I've recommended someone return their personally-owned 1911 to the manufacturer for examination and repair due to one reason or another. :whistling: