Week 11 should be around their previous max. The last week, a new max might be attempted. By slowly working into singles, the lifter can build momentum and confidence for the meet while still building strength. This 12-week routine is just one example. More experienced lifters may not need as many weeks.
Some lifters can get by with little or no singles during a contest prep period.
One thing to keep in mind is that a single rep is very strenuous for both the mind and body. Too many singles can burn a lifter out before the meet. 1-2 singles per workout may be all that's required. As I mentioned earlier, there is fewer margins for error with singles, so great attention to form, spotting, and lifting safety must be exercised. If you practice these items on ALL your sets and reps, the heavy max ones will be easier to perform in the safest and most efficient manner.