It’s not a fight. It’s conditioning a response to pressure, that isn’t “screw you.”
My fjord is level headed, sensible, and compliant 99% of the time. That 1% he isn’t, can turn into fast fireworks (emphasize on both fast and fireworks) and that has happened when too much stress has been put on him. A horse like him, you aren’t going to win a tug of war match if he decides tugging in a trailer situation is too much. I learned this lesson lunging and twice had a runaway horse and broken equipment. It’s the whole rabbit thing for the WS fans. I will not win a tug of war if that what it escalates to and it could with stress.
We have had no fights with trailer loading and he has gotten on willingly every time I have asked and most recently just walks right on. Not getting on is not an option.
We do groundwork regularly for fun and for reasons like lunging and trailer loading. With working equitation, he is exposed to and excels with many different asks and tasks. In a low stress situation, responding to pole pressure is no big deal for us. In a stressful to the horse situation, I have had to learn a different way to get the end result. The different way is to not put too much pressure/stress on him and/or de-escalate when I see his stress signs that are going to lead to a much bigger problem.
The WS methods have worked well for me. Many horseman think it’s the work of the devil some of the methods WS uses. To each his own I suppose.
I personally prefer the outcome of WS methods over more traditional methods. YMMV
I understand what you’re saying, but I interpreted @FjordBCRF’s statement to mean that she looks for small signs of stress and adjusts her approach BEFORE she ends up with an “eff you” response. I think that’s quite smart and more likely to result in positive experiences (and ultimately, in a reliable loader) than powering through the stress and getting into a tug-of-war, especially with a breed that can easily turn into a tank at a moment’s notice!
ETA: I first subscribed to WS last year in response to an incident where my young horse would not load with the usual methods and escalated pretty quickly to rearing and leaping. After several weeks of WS groundwork and no specific trailering practice, he loaded just fine even though trailering still makes him anxious. It’s been very helpful to both of my riding horses in general.

I interpreted @FjordBCRF’s statement to mean that she looks for small signs of stress and adjusts her approach BEFORE she ends up with an “eff you” response.
Exactly this!