Final 3 Greens
I take your point that 3 to 3.5 deg is shallower than a lot of people fly SEP aircraft and I nearly put 400 to 450 feet per mile. But I decided that the shallower angle is what I would recommend for the case where somebody is going to have their first go at a grass field, perhaps solo. For this first approach it is more important to get the approach and landing right rather than be in a position to glide the rest of the way if the donk should quit.
I feel that shallower approaches give the best and most obvious cues about the angle you are flying and that the steeper you get the harder it is to judge the angle and so the easier it is to arrive at the flare point much steeper than you realised.
Once a runway pilot has overcome the ‘newness’ of setting up the approach to a grass field then like everything else they may modify their technique based on experience.