Just because the system allows it doesn't mean the casino is to be held accountable when someone exploits it, willingly or accidentally. It is the player's sole responsibility to read and to understand the rules and the T&C's, and I assume this is what eCOGRA too were referring to when dismissing the complaint.
Besides, any casino or bookie also have in their T&C's a protection against errors, be it human errors or flaws in their system, once again leaving the player powerless as this protection pretty much says: "We can do whatever the ***** we want if it pleases us or if you annoy us"
Nitpicking about the wording in the very straightforward max bet rule surely puts the player at risk of ending in the "if you annoy us" category.