@Catherine1216 Often the Help articles aren't updated when things change on the plalform. It's possible that the non-refundable discount option on your screenshot was introduced after that Help article was written and may be cumulative with other discounts.
I've never heard of a seasonal discount, but that doesn't mean it doesn't exist.
One thing you should be aware of is that the non-refundable discount doesn't seem to be a great option for hosts. I've read several posts concerning CS reps overriding the non-refundable policy and refunding guests. As long as they might do that, non-refundable doesn't mean much.