The IBD 200 list is essentially top 200 stocks ranked by IBD composite rating. If you look at the rating closely, it has higher weights to relative strength and sector relative strength. You will notice if a sector has high relative strength, even a 65 EPS rated stock will be in IBD 200.
The other thing to note is all the stocks on Thursday would be around 15% of their 52 week high or recent high in case of IPO. As a result in IBD 200 you get stocks which are in last stage of rally, some midway through and some stocks which are consolidating or correcting. The reduction method should find the third kinds.
65 Day price growth is one way to do that. It gives you a very few candidates to focus on. You can try 33 day price growth. It is more suitable to swing trading. Anything less than 20 days may not be very useful.
Also the patterns like cup with handle, pullback to 10 week MA line, double bottom at top of range, flat bases etc, which are popular patterns in IBD methodology, you will find them only in stocks with low 65 to 30 days price growth, not on overextended stock. Even if you find those patterns on overextended stock, chances of their failure is high on those stocks.
The number of opportunities you get is function of market phase. If you see the list after a 2-3 months market correction or more, you will get lots of opportunities. After 2to 6 months of rally , you will get few opportunities.If you consistently trade the IBD 200, then you would anyway would have bought the breakout on the overextended stocks on 65 days scan long time ago if at that time they were member of IBD200. Probability of that happening is high because you are constantly getting in IBD 200, top 4% stocks ranked by composite ratings.