Good observation. Both devices carry a 1500mAh battery and both use USB-C, but the Pro 3 charges at a higher amperage than the Go 2. That higher amperage - more current flowing into the battery - is what gets the charge done in roughly 30 minutes for the Pro 3 versus 45 to 60 minutes for the Go 2. The trade-off is that fast charging generates more heat in the battery and over time it can reduce lifespan slightly, which is why the Go 2 uses a gentler charge rate that is still quick but prioritises battery longevity. Neither is wrong - the Pro 3 prioritises speed and the Go 2 prioritises battery health over its lifetime. Any USB-C cable and plug you use matters though, for both of them. A cheap charge-only cable will trickle slow regardless of what the device wants to do, so if you find a Pro 3 charging slower than expected, a known good data cable and a proper power adapter often solves it immediately.

Never thought about the amperage difference being deliberate rather than just one of them being better. Makes sense that the premium device would prioritise speed and the value device would prioritise the battery itself.

That explains why the Pro 3 takes half the time. Good to know it is not a fault on the Go 2 then, just a different design choice. Cheers.