If it's a properly done cheese steak, and it's not sliced in the same direction as the grain of the meat, he's probably right.
It's quite possible that a cheaper cut of meat would have a "beefier" flavor, just because many of the tougher cuts of meat tend to be more flavorful, partially because of the fat content.
All of that being said, it's really a matter of personal preference. Some of of the places near me use the equivalent of "steak-ums" and not everyone's a fan of the texture. If you want to find out if it's worth it for you, get a few friends together, order two subs with the same toppings, one with the upgraded meat, one without, and do a taste test. (and if you can, get one person to order it and label the packages, then hand off to someone else to portion it out, so it's at least closer to double blind, particularly if they use two different labeling schemes)
update : Unlike chicken, beef doesn't have the obvious distinctions between light & dark meat; the normal rule is that the further from the hoof and horn it is, the less that muscle group has worked, and thus the more tender it is ... but as with chicken meat, it's the working muscles that tend to be more flavorful (although tougher cuts). And as with chicken, it's the fattier meat that has more flavor.
Some cuts of beef have the grain run in one direction -- because of this, we can cut the meat across the grain, which tenderizes it. It can be done before cooking, as with philly cheesesteaks, or afterwards, as is done with fajitas. Common cuts used for this sort of treatment are flank steak and skirt steak, which may be difficult to find in all grocery stores as so much seems to be diverted for restaurants.
Besides cutting, other aspects of processing (eg, aging) can affect how 'beefy' the meat is.
I would actually recommend the opposite of what was said above. Since the meat is so thin you may have much better results pan searing it in an extremely hot pan from slightly frozen. This way the outermost layer will start to undergo the maillard reaction long before the inside of the steak reaches a medium-rare temp and will give you a better chance of preventing it from overcooking.
This link provides an overview of the process for a much larger piece of meat then your using but the searing process is what your concerned most with since your steaks are so thin. You will likely have to play with the timing a little bit with regards to how frozen the steak needs to start out but I figure erring on the side of too frozen is best since you can then heat them in the oven to the internal temp your looking for.
http://www.thekitchn.com/for-the-perfect-steak-first-freeze-it-solid-then-cook-for-an-hour-165793
Best Answer
James Salisbury was an American physician and chemist known for his advocacy of a meat-centered diet to promote health, and the term Salisbury steak for a ground beef patty served as an entree has been used in the United States since 1897. Today, Salisbury steak is usually served with a gravy similar in texture to brown sauce, along with various side dishes. It is a common item in supermarket frozen food sections.
Dr. Salisbury recommended this recipe (somewhat different from modern Salisbury steak recipes) for the treatment of alimentation: