First, even though there are, generally, no physical limitations in pool, there are varying degrees of natural ability. For those with less natural ability more work is required to reach higher levels. There are, quite likely, many very knowledgeable instructors who, for whatever reason, do not have the time nor the inclination to put in the amount of work it would take to reach pro speed. They very well may also have neither the time nor inclination to involve themselves in tournament play.
Assuming we're talking about instructors affiliated with an organization like the PBIA (formerly BCA) or ACS they are likely providing accurate information to their students. Depending on their level of certification, playing ability, and experience they may or may not have much to offer a player of much greater ability than their own. However, it is quite likely they can offer something, even if it's the contact information of another instructor better suited to help said player progress.
Assuming we're talking about instructors affiliated with an organization like the PBIA (formerly BCA) or ACS they are likely providing accurate information to their students. Depending on their level of certification, playing ability, and experience they may or may not have much to offer a player of much greater ability than their own. However, it is quite likely they can offer something, even if it's the contact information of another instructor better suited to help said player progress.