Well if you are booking at exactly 11 months to your check in you either can or can't book your entire reservation that day. There is no partial booking that would be possible. So another person walker or not was simply quicker to booking your check in day. If it is truly walking a simple day by day waitlist approach (waitlist the 11 month day each day, likely it will fulfill the next day early in the morning) will help you get the room (and stalking the site even helps more)
As for short notice trips that simply isn't the nature of a timeshare and DVC was a bit different, from my understanding, in the beginning but it should have always been expected that a timeshare requires months in advance planning and/or extreme flexibility. I rent a Vistana timeshare quite frequentl. Likely shorter trips are getting harder to find for many reason: 1) Easier visibility into available rooms leading to maximum point usage, 2) renting leading to maximum point usage, 3) Disney in general requires at least 180 days of planning if you want that dining reservation, 4) cyclical nature of festivals and parties (which are increasing popularity), and 5) an extremely healthy economy. But none of the reasons for short notice trips being harder to get is because of walking. I would even say people being told buy where you want to stay (which is great advice) is leading to less availability at 7 months because people book right at 11 months and are happy where they are at.
Now I'm not a fan of walking but I did buy-in realizing right away the loophole existed and mentioned it during the sales pitch so I can't complain too much. But I really don't like it because it really is a self-driving system. People walk because they see availability disappear right at 11 months so they grab when they can which leads to more availability disappearing scaring more people; plus I think the boards and other similar places mentioning it as being necessary don't help either. But MS does know about walking doesn't care and in fact they bring it up to some, by accounts on here.