Yup. Even if the event miraculously doesn't gets cancelled, it's better safe than sorry. Also, it probably means double the payday. Paid for the work now and maybe for the rights usage later if they use it next year (if that's how it works, unless Uni owns the exclusive rights, but I doubt it since Figure owned his own stuff he made).
All things considered, that's the best way to look at it. All the work that has been done this year has already been paid for, including a lot of the stuff in the future. The only thing that hasn't been paid for is the actual staff to make things run. I can't imagine Uni will throw everything away, so anything that doesn't get used this year, will most likely be used next year. As for the rights to properties, that might be tricky, but I ASSUME there is insurance for this kind of thing and exceptions in the event of cancellation. Unless it's a very prickly property, at the least, any maze that is already built will probably be repurposed (think Scream at HHNO turning into Purge).
Will they let the mazes sit dormant until Sept 2021? I'm not an expert on the subject, but these things aren't built to last all year round and through constant weather. Knotts often lets some of their mazes sit around, so I do think it's possible HHN can too. Maybe they'll be more proactive to store them in a location to keep them more safe though.