I'm not saying it isn't 'A' factor, just not 'THE' factor, and certainly not a 'huge' one. Everyone is hiring for the season. Confidence has improved with things opening up and dates firming up. Everyone 80%+ is getting ready to try doing more normal things again.
Few people volunteer to leave a job right before christmas, so the timing is going to be an impact, but the hiring of xmas staff (who do meet the requirements) means they just hire a few more in the mix, and can choose from a wide selection to replace those they lost. They were about to do bulk recruitment and bulk training anyway, what's a few more people in the room?
I think 10% is being extraordinarily generous. The uptick in vax rates post-announcement suggests the current states include a lot of 'hesitaters' rather than outright objectors. For those who weren't early adopters, there was no real reason to go out and get it - until 9 November. Now there is a reason.
The park (and many other employers) will lose a few strong objectors, but most people who have jobs will choose a paycheck, and if the park loses more than 2-3% i'll be very surprised.
Circling back to the crux of this line of discussion, I disagree that the park is 'about to stand down a lot of people' or 'have a heap of roles to fill' because of the vax restrictions. I suppose it depends on what you consider 'a lot' or 'a heap'.