No, I don't think it's a joke from the club at all.
The club are obviously trying to attract fans who could not make the original dealine date.
Maybe with being 10% up on the same time last year they will know how many are renewals and the number than are rejoining, this is another way of getting more fans to games.
I'd imagine the swipe cards are at the club and they feel confident that all those who renew or rejoin by 12th December will get their season card ticket by Christmas.
Just a personal POV but I think the Marketing at Wigan RL is absolutely brilliant.

If they're existing season ticket holders, they're already attracted. Anyone that couldn't make the deadline date, having had about 8 weeks probably isn't going to renew. Unlike jackdog who stupidly left it until the last day.

Thanks for your comments, 'clever', patronising and and insulting included. You are all obviously rolling in money. Maybe you also have to pay for only one season ticket?

I actually agree that this is annoying from the club although it does happen most years

Due to unforeseen car issues, I couldn't afford to pay for my ST upfront so had to opt for the repayment option. Although this option is interest free and can be paid off early, using it has meant I had to pay an extra £20 "admin" fee and will have a search record on my credit file for the next 12 months

I'm not a fan of the £20 admin fee, with the most expensive tickets it's over 20% APR and increases as a percentage as cheaper tickets are purchased.

A £228 ticket on a credit card, paid off at £21.12/month for 12 months at 19% interest would cost £253. I'm not sure where I see value in the "0%" deal from the club.