Isn't that what other Triple Crown winners have gone through?!?
Secretariats top rival was Sham...who ran all 3 races,,,Seattle Slews top rival was Sanhedrin...who ran all 3 races...and Alydar ran all 3 races against Affirmed...so, who knows.
You also have a valid point, but consider that since probably Secretariat, someone(s) have been thinking about ways to game the system. Horse people are like that - I know.
Once upon a time the crown was run by horses that went the whole distance. Not so much any more, for various reasons. Mostly money related.
And putting fresh horse into a race that haven’t gone the distance, is well, not Kosher. IMHO.