No, I walked from where it says 'Low Auchengillan' to '51' along that winding path- which is a defined path bounded by trees and shrubs. The Outdoor Centre is on the other side of the road.
I'm inclined to think he just doesn't want to see folk passing his house and tries to deter people by claiming that they're trespassing.
With lockdown and the new St Mocha coffee place it no doubt has increased interest in the surrounding area and no doubt it's probably annoyed him.
I've actually found a walk report which actually details a walk in the local vicinity along with pictures, so it seems that due to a few well placed 'Private' signs and an fellow that seems to want to keep the area to himself, folk may well be missing out on an very enjoyable walk.
You can check out the details here. I'm looking forward to enjoying it.
https://www.caingram.info/Scotland/Pic_htm/auchineden_hill.htm