When adding old wired sensors in an open loop, does it matter which wire the resistor is wired in series with?
A little clarification, are you asking about Normally Open sensors? What do you mean by open loop?
If a sensor is Normally Open the resistor would be wired in parallel, not series.
If you are just referencing a Normally Closed security sensor zone, no, neither the wire nor the terminal where the resistor is connected matter, so long as it is wired in series and connected to one terminal.
Generally for consistency you would wire them into the - side.