I'm all in on cynical behavior on Wyndham's part but I would have thought sixty days from yesterday or the day before yesterday would have been more desirable check-in dates -- Friday and Saturday, 12/21 and 12/22, rather than Sunday.
Actually for people driving any distance especially coming from the North or other areas with possible winter weather issues the Sunday check would be better for that week. Even if I was flying I would still prefer it if I was coming from to going to an area that might get bad weather. If you were driving and it was a good distance you would have to leave after work on Friday and possibly drive through the night for a Saturday check in. With a Sunday check in, driving or flying, if the weather is good and you can get there on Saturday, that is fine you just make sure you have hotel or motel reservation for that night and if you won't need it remember to cancel it in time. If the weather and driving conditions are bad or the flights on Saturday are cancelled and you don't get there until Sunday you haven't lost the first night of that expensive holiday week vacation you paid for.
When you live up North you tend to like going someplace warmer during the winter. I've lived in Florida for 7 years and it still isn't long enough for me to forget the cold, snow and ice! Or how I took the weather into consideration when planning winter trips.
I lived Ashtabula, Ohio in a town on Lake Erie until I was 21, in Erie and Edinboro, Pennsylvania until I was 38. We moved into the house in Edinboro on December 4th and never saw what our yard looked like until the snow melted in the Spring. The winters of the 70's and 80's were hard ones. For the next almost 22 years we lived in Butler, PA which by comparison to Ashtabula, Erie and Edinboro seemed like it got hardly any snow at all. There we got ice on the roads which is much worse than snow for driving conditions. Several years we went to the Outer Banks for that last week of December. One year was warm enough not to be chilled when we got out of the hot tub on the deck of the rental house. Another year it was cold enough to wear our winter coats when we walked on the beach. That year there had been one heck of an ice storm that hit part of Virginia the day before we were driving through. Everything was still coated with ice, it was beautiful. We saw a lot of trees down and some places were still without power. The driving conditions weren't great but at least the roads were open and we were able to drive.
Before we moved to Florida for 6 or 7 years we went to Las Vegas in mid March. For some of those years there was a convention for my job and our anniversary is St. Patrick's Day. Some years I spent a lot of time looking for a flight with no layover and a good price. It was easy to find flights with layovers at better prices but I held out until I found one with no layover at the the same price or close to it. The layovers were in Detroit, Minneapolis or Chicago. One year my husband got exasperated with me, told me to quit obsessing about a layover and just book the darn flight. I told him he'd gotten soft from living in Butler for so long and forgotten that there was usually an Ides of March or St. Patrick's Day snowstorm. That I didn't want to take a chance on being stranded in an airport and lose a day or two of our trip. One of the best I told you so moments I've ever had with my husband was when we were playing at a blackjack table and talking to the other people at the table. The guy at third base was really unhappy because he'd lost two days of his Vegas jaunt when he got stranded on a layover in Detroit due to a snowstorm. I mentioned that in the areas we were from people either called it an Ides of March or St. Patrick's Day snow storm. The guy responded that that's what he called it too and that he couldn't believe he was stupid enough to book a flight with a layover in one of the cities I mentioned even if it was cheaper and that he'd never do it again. When my husband and I quit laughing he explained to the guy that would have been us too except that once again he was grateful that I usually don't listen to him.