+1, chainstay length has no impact on gear ratios.
Taking it from the pedal to the rear wheel contact patch on the ground the things that impact gearing, force, torque, and tangential velocities at either end of the system are:
- Crank arm length
- Chainring radius (for which number of teeth is a valid proxy given a constant chain pitch)
- Cog radius (again cog teeth is a valid proxy)
- Rear wheel radius including effects of loading the inflated tire with the rider aboard the bike
Those are the effective lever arms in play and from a gearing and leverage standpoint it doesn't matter if those lever arms are connected by one meter of chain or ten. From a drivetrain efficiency and loss in the drivetrain standpoint you'd likely start getting higher frictional losses with extremely long chains, especially once you added roller tensioners to keep them from sagging but it'd be negligible if even measurable for the kind of differences you'd see between a short and long chainstay bike.
-Dave