I don't think you can book AND travel in the last four months of your use year. My use year is DEC. So I could not call Oct.1 for dates 10/28-11/06. I would need to make those reservations before August to travel those dates.
The rule of four does not apply to the DVC resorts. You can book and travel any time, as long as you have points. So, in your example, if you called Oct. 1st to book at BLT and there were rooms, you could definitely go 10/28.
That only applies to those in the Disney Collection, World Passport, etc, (except
Disneyland).
But, the OP, your UY is important because you want as much flexibility as you can have to cancel or change a vacation without losing points.
When you have a UY right before the start of your vacation, and within your banking window, you have a lot of options if you have to cancel (31 days or more). You can rebook the trip or bank the points.
Even if you want to change a vacation, traveling during those first 8 months allow for this. I have a June UY and travel in early August. I have up until 31 days before the trip to make changes to the reservation and not worry if it takes less points.
If I was outside that window, the only changes I could make would be for vacations for more points, or risk having a short timeframe to use the points up.