Greetings,
A database of blades, including side views, would enable anyone to compare a player's blade and identify what blade they're actually using. The plies would give the definitive answer - regardless of the handle.
The conundrum about sponsorship is certainly perplexing.
Perhaps clothing is the main aspect for some, whilst the manufacturers may have a "gentleman's agreement" on equipment: whoever's handle (brand/logo) is on the blade gets the PR benefit!? It's also possible that a player may be more comfortable with a particular handle rather than the one that comes on the blade - like handguns, no matter how well engineered are the internals, if the grip isn't right for you...
Kindest regards,
James