OLM's vary significantly in their design. Some, like the Toyota one, are just a basic mileage counter. These are obviously the least accurate, others, like the Stellantis and GM ones, vary the interval based on parameters like operating temperature, speed, hours, oil temperature, number of starts...etc that more appropriately captures and accommodates the operating profile of the equipment than just dumping the sump every x number of miles.
Again, depends on the operating conditions. An engine short tripped for 3,000 miles could have considerably higher contamination levels than an engine with highway miles driven 10,000 miles.
Yet a surprising number of people are comfortable running rock catcher style filters
Which are all pressure-lubed, so I'm not sure how that's going to impact anything?
Sure, but let's try and make that an educated decision not one based on feelings.