I appreciate that they laid out their thinking on the subject; too many don't. Looking at their listing:
1.) It's a local standard of practice? Not a good basis; not everyone is a lemming. If solo diving is prohibited in a blanket fashion at Florida state parks, that's something that ought to change, not be duplicated.
2.) Solo training doesn't cover solo diving in caverns. Okay, if most of the diving there is cavern diving (is it?), that makes sense when relying on a recreational solo cert. Then again, OW training takes place there, and that's obviously not cavern diving.
3.) Too many solo divers 'fail to follow the rules.' It's worth noting that 'rules' required in a course tend to become recommendations when certified adults head out to dive on their own. Not binding rules/laws.
4.) It sets a poor example. Oh, I'm sorry, does diving not looking like a bubble wrapped lemming set a 'poor example' for OW students who might look over and see you solo diving? And OW instructors shouldn't have to explain that? Perish forbid they find out solo divers exist.
Then they close saying buddy diving is the norm for recreational divers, it's what you learned as a beginner, it's the standard they follow.
Perish forbid you might've grown and changed since your OW course. Where we also learned it was recommended we not go over 60 feet deep.
So, out of all that, I see one item that looks persuasive (and the one item may be good enough). The rest reads like grossly over conservative 'Big Brother' overreach and a tad condescending.
Wonder how much of this is really fear of lawyers?
Their hole of water, their rules. Perhaps a few more people will choose not to be their customers.