I can think of a few reasons:
1. A high end, high efficiency filter traps more particles, especially small ones, faster. Net result is insolubles and other gunk spends less time circulating before getting trapped by the filter. This is a good thing in and of itself.
2. A higher end filter allows more flexibility in your OCI. There's a built in confidence factor that means regardless of what you had in mind initially, you can push the OCI longer and not have to second guess whether the filter will make it.
3. Tying into the above, you can opt to just change the oil and leave the filter. I know this is blasphemy to suggest doing an OC and not putting on a new filter at the same time, but at one time so was anything longer than a 3mo/3k OCI. Newer data suggests that, to a point, filter efficiency increases over time; meanwhile, oil life continues in a (non-linear) downward trend as tbn depletes and the additive package gets worn. The oil life may be gone, while the filter is only just broke in.
The new thinking is that you don't have to match one to the other and change them at the same time. They are two independent variables in the same equation and its perfectly fine to assign different values to each as long as the math adds up.
So yes, tossing a M1 filter after 5k is a waste. But you don't have to throw out the bath tub with the bath water, or replace the filter just because you elect to use an oil and run it for 5k.
My M1 filter was put on part way through my previous OC, so its still in use and doing its job on this second oil change. If there's still lots of life in it, it'll see a 3rd cycle of oil through it, and if it does, it'll be changed part way through that OCI - to another M1 EP filter.
This is backed up by findings from the Neptune study on the effects of OCI intervals, top up oil on OCIs, and the effect of changing just the filter during an OCI; and other studies showing that - to a point - filter efficiency increases over time.
-Spyder