Why are the Fidelity Select and Fidelity Equity Ratings Different?
Why doesn't the Select System trade the highest ranked Select Fund from the Equity Fund system rankings?
The simple answer is that the systems use two different ranking systems.

The Select system can trade after only 30 days, and it also can rotate into cash if needed, so it looks back a significantly shorter time period than the Equity fund system.

The Equity fund system only trades every 90 days, (this is done so it can use many more of the Fidelity offerings, especially several of the international fund offerings).  In addition, since it has a 90 day holding period, we chose not to try to rotate into cash.  Because of this the system not only looks back over a longer period of time to rank the funds, but the volatility of the funds is weighted more heavily.

The Select funds tend to be more volatile since they  are by design focussed offerings, so funds that are at the top of the Select rankings will not necessarily be at the top of the Equity fund rankings.