In the wall switch box the wires are both black, but one is load-side and one is hot-side. This is supposed to be a single-pole GE 15071 switch, and it would be replacing a single-pole manual wall switch.
I could understand the need for 3 wires + ground if this were a three-way switch application, but the box even says "Single Pole (Controls lights from one location)".
...so I would be looking for white neutrals elsewhere in the box, correct? This is a 3-gang box with a few wires behind the switches wire-nutted together and I'll check whether there's a combined white/neutral if that's the direction you tell me.
I took the timer switch back out and replaced with the previous switch so I could restore power (unfortunately my PC is on the same circuit as this light/switch). So once I hear back from you I'll complete the transaction/payment, shut down my PC, and look for white wires behind the switches. Thanks Jason.