The issue I've encountered with plastic fenders and the listed clearance is this:

The mounting bracket for the struts is on the inside of the fender, reducing the actual clearance (which is measured for the plastic fender itself. So if you think you're within 5mm total clearance, you could end up 2-3mm shy because of that bracket.
I have seen people with my rando club who have drilled the rivets and moved the strut brackets to the outside of the fender to use 35mm fenders with 30mm tires. It's not the prettiest solution, but it increases the clearance (as long as you put the buck side of your rivet facing out, not in) and it doesn't present a gathering point for road grit, mud and other debris to clog the tight fender line.

I prefer a 10mm minimum clearance on my fenders, and use a 48mm stainless fender over 32mm tires.