PDA does exist, but it's very rare. In a 20+ year career I have seen true intractible PDA 2 or 3 times and hundreds of autistic kids whose coping style was avoidant.
Demand avoidance in autism is common, linked to an unempathetic environment, sensory overwhelm, or an avoidant coping strategy.
This is all research based (Pathological Demand Avoidance: symptoms but not a syndrome - PubMed https://share.google/POsPEf17ikPkmXFKA)
People confuse the two and think any autistic child with demand avoidance has PDA.
FWIW I have a demand avoidant adult autistic child myself, and in adulthood low demand parenting/interactions have worked very well.
Every parent must have red lines: usually based on health or safety. Eg I have yet to meet a "PDA parent" who hadn't managed to get their PDA kid to wear a seatbelt in the car.
Then you have the "doesn't matter enough to force it" issues - like insistence on aspects of uniform that are a sensory nightmare. Imo schools should make adjustments here
Then there's the grey areas - life skills, education. I do think this is going a bit awry ATM and I do think that it connected to the curriculum, academy chain behaviour policies, an overly authoritarian education system. I think as parents we have to balance what our kids can manage, bear in mind that often, the less they can do the less they can do as a vicious circle, watch out for their world narrowing too far, and use specialist interests as hooks back into life wherever possible. And don't assume that demand avoidant behaviour in autism is a whole different syndrome and that your child is pathologically incapable of compliance. Most likely they can comply - where they perceive a need or a reason, where they can manage the sensory aspects, and where they feel understood and appreciated.
I personally think the name PDA is unhelpful. Just think of it as a person who manages anxiety by active avoidance, rather like a person who never goes abroad because they are scared of flying, only this active avoidance spreads into more and more areas of their life. Gentle graded exposure is still incredibly important.