It this a new approach to accessibility requirements and conformance or really just a maturation of where industry is at?
It is a new approach in a couple of ways.
First, you are correct, it is designed for non-technical as well as technical people to read and understand the main points. It is designed to be a guide for many more industries other than just web design as so many things overlap nowadays.
Secondly - the new scoring system is far better, a site with one contrast error is currently considered to fail WCAG 2.1 AA which is pretty ridiculous, the new scoring system introduces bronze, silver and gold tiers (and bronze is equivalent to current WCAG 2.1 AA in terms of difficulty to achieve from what I have seen so the scoring is strict with more room to "excel" and set yourself apart when you go the extra mile).
One thing to note is the assessment criteria does not "gives some flexibility and room to move when assessing an application's compliance to the guidelines." as you said, the idea is the exact opposite.
It is designed to be a lot more clear what constitutes excellent and what is poor instead of the current A, AA, AAA system and the new testing guidelines are designed to remove ambiguity and interpretation.
If so, are there examples of organisations that are implementing accessibility guidelines and standards that are in line with WCAG 3.0 already?
With 5 published partial example guidelines that are not fully fleshed out it doesn't give people much to go on, especially as 4 of them are pretty much the same as current WCAG guidance.
"Clear Words" is a new one that my company already kind of uses when advising clients on writing copy. We use the rule "reading age of a 12 year old" to help people simplify their language choices as 1 in 5 adults in the UK has the reading level expected of a 12 year old and encourage people to use tools such as the Hemmingway editor to check for long and complex sentences etc.
The other rules are basically current WCAG rules repackaged so everyone should be using those already.
I think that is about as far as I can stretch to anyone using the WCAG 3.0 guidelines today!
Should I be trying to implement WCAG 3.0 today?
To quote W3C:
WCAG 3 is not expected to be a completed W3C standard for a few more years. And, for at least several years after WCAG 3 is finalized, WCAG 3 will not supersede WCAG 2 and WCAG 2 will not be deprecated.
It is still going to be several years before WCAG 3.0 is released so don't worry about it yet, trying to do anything to prepare for it now is quite futile, just follow best practices as they stand today and you will be fine.
WCAG 2.2 is where you should be focusing your attention for now
WCAG 2.2 is far more appropriate to "worry" about as that is expected to land somewhere around summer time. If you are trying to get ahead of the curve then start with these items, especially focus indicators as a lot of sites do not comply with that under current requirements, never mind the new requirements.
The new criteria include:
Fixed Reference Points
Focus Appearance (Minimum)
Focus Appearance (Enhanced)
Pointer Target Spacing