Barring a catastrophic failure of some sort, there really isn't a source
for a lot of harmful contamination inside an automatic transmission. The
main wear product is a very fine "dust" from the lined clutch plates and
the bands. Its not big enough to clog the valves in the valve body, and
 having it carried back into the clutch packs doesn't do any harm since
its the same material that they're made of anyway. The planetary gears
are in constant mesh, so they don't ever shed chips to the same degree
that gears and synchros in a manual transmission can. And finally, the
tolerances of the valves in the valve body are known, so a wire mesh
that will trap the biggest particle that could potentially jam a valve
is all that is really needed.

That said, some manufacturers did always prefer a finer filter to trap
some of the clutch dust. It can potentially wear things like bushings
and thrust washers, but not very badly. And it depends on the materials
chosen for bushings,, bearings, and thrust washers, too.

And probably the best way to improve overall trans fluid filtration is
to do what some companies (Chrysler comes to mind) did for fleet
applications many years ago: take the fine filter OUT of the pan, put a
mesh screen there, and then put a full-flow  replaceable cartridge type
filter (like an engine oil filter) in-line with the cooling lines. that
allows a fluid and filter change without dropping the pan, and the wire
mesh filter will catch any stray large chips that do form for whatever
reason.

design flaw, www.aa1car.com/library/2002/bf90222.htm para 12

1 can fit a filter ( e.g. Mazda 323's petrol filter ) onto the joint
( betw metal pipe & rubber hose ) of a-t-f's cooling ( return )
pipe ( cooler than exit pipe ).