Clearly the binary extremes do exist: an early stage start-up with an MVP in beta trials does not have PMF and conversely, a longstanding dominant product in a mature market will(currently!) have achieved PMF. However, I would suggest that there is a large grey area between these extremes and that PMF is not a binary concept. No matter how great the product, the target market won’t stand still and neither can the product. It is therefore an ongoing, iterative process and most scale-ups will continue to overhaul their products for many years after they have apparently achieved PMF. PMF is therefore a transient concept although market dominance at scale will protect incumbents.
There are several metrics that demonstrate whether an enterprise has achieved PMF. Clearly these can be useful, but the pursuit of generic metrics (and aggressive growth) may not be the right strategy for a start-up, where instead they should focus on establishing a sustainable, profitable business.