I'm not more qualified by any means, but the answer as I understand it is about geography. If you find wrecks within the leased area that are not 1715, all the same rules apply. Why? Because no one knows with 100% certainty what wreck is what. Maybe a 19th-C ship was carrying old coins & wrecked. Maybe flotsam brought some 1733 artifacts up to Ft. Pierce. There's no way to know, so the contracts cover it all regionally.
Something to do with outgoing/incoming tides re: metal detecting. You can metal detect basically to your ankles in water most days, but I'm no tidal expert, so take that with a grain of saltwater.
If you see something through your glass-bottom boat, admire it. Legally, don't touch it unless you have the contract/lease.