The issue I'd see is that your be forcing trades probably. It's better to have a setup and wait for it on multiple instruments.
If you have 3 stocks let's say, then how often are they range bound/mean reverting? Do you have a setup that can capture these whipsaws in a range? If your more of a trend swing trader, your setups might not come as often as you'd like with only 3 stocks/ a sector and sectors can be quite correlated a lot of the time and I find myself picking etf's in this scenario.If see the same setup in multiple stocks of the same sector.