Toadi a lone province can take acres from your KD but he's not a threat to you
In my book a threat is someone who can take cares from my KD. It is an even bigger threat if I have to hit 5 or more times just to match a single of their hits. Lone provinces are huge threats for top KD.

It's true that a loner can take acres by abusing GB protection (which is the real problem, not KNRG).
KNRG and GB protection stacks up perfectly to pretty much nullify top KD gains. GB protection can get gains down to 20%. KNRG to 67%. Both stacked, the loner suffers 13% of normal losses. That's 8 hits to make up for 1 of their, instead of only 5 without KNRG. Nevertheless you are correct, GB is the most important factor here.

Nevertheless, when doing a single hit, you have to make sure that nobody in the KD you target can retal you, mostly because of KNRG. If I find a juicy T/M I will always hit there, unless there is an attacker as backup (at least for a while). Since you do not want to find someone who can retal you, then you have to go deeper in NW - KD and province wise - to find safe hits. If KNRG were removed, I could gamble on a hit of the T/M, because at worst I risk losing what I grab. Problematic, but not too bad. Because of KNRG, a KD mate could lose 150% of what I grab, and that's not an option. If KNRG was removed I'd bottomfeed way less than what I do when whoring.