You are going to get answers as diverse as the color and contents of the containers of lubricants in the long rows at WW.
Gotta factor several things into the answer including product likeability aka joe blow spreading the word how he likes his widget, liability, design preferences, company's equipment history, usage in environmentally unique situations, choices of equipment make-up ratings by the OEM, specific design margins due to "anticipated" usage on and on.
Go to a site like WIX where specs are posted and just grab a handfull of filter numbers and run them through. Notice what makes the difference in the number. Usually it's outer dimensions which need to be considered in different equipment because of possible fit interference with other parts of the machine. For SAE there is a standard thread size (3/4-16), for metric another (forget #), filter media entrapment (micron rating) has a lower limit to be a full flow filter so there is a bottom limit to that, but there are numerous types and other things like bypass valves or not and on and on. Bypass valve ratings are pretty constant, some use a silicon seal (never had a seal fail on any filter). I have dissected used filters that I have had in service for years attempting to see if one over the other has any degradation as a result of materials used or construction techniques and found paper survived as well as metal for things like end caps and the media remaining intact whether it was fabric reinforced or not.
I went through my recommended filter list for my equipment one day and other than SAE vs Metric for threads, I had 2 filters that met the SAE specs for all my equipment of various kinds including my truck, and 1 for Metric.
On initial drain interval it's good design practice to ensure that leftovers from the manufacturing process are removed from the machine. This very well may have been leftover from eons ago when engines didn't have filtration. Course I have yet to find any in any new equipment I bought. If you are worried about it, put a magnet on the bottom of your drain pan and it will take care of any steel which would be the most damaging component since other than the piston material and mains (which get filtered pressurized oil) steel/cast iron is what the engine is made of and any alum shavings would be of little damage. Course you have to get them out of the sump first and they will resist that.
So just like not getting all worked up over what's in my owner's manual, I do what I want within reason and guarantee you my equipment will be here long after I'm gone. But everybody has their "drum beat" to which they march and nobody is about to change their ways so that's the way it is. So expect a diversity of answers on this one.
Good luck in your search.
Mark
