Those experts and stakeholders have a day job (i.e. don't have time to do this) and are usually in silos. They are not experts in workshop facilitation, user testing, usability, rapid prototyping to iterate on ideas and to think more broadly.

It helps to avoid parts of the innovator's dilemma and to break out of siloed thinking, i.e. involve stakeholders from other functions of the org.

Not sure what you've been sold, but there are no special rules or rigid methods.

But you're right, unfortunately there are consultants who use this term to sell you a new wunder method to solve all your product problems, but they are not really design practitioners.

Same way as people took the Agile Manifesto and bastardized it to create SAFE.