It's unfair to compare an idling deep sleep device with a cold boot.
However, there is a shortcut: Just don't boot a full OS (thinking of custom firmware which boots in fractions of seconds, standard in the Microcontroller world). Or boot an optimized Linux user space. I am confident with a bit fiddling one can bring down a standard SBC Linux to a few seconds from cold to ready.
Functional comparisons among devices within a category are always fair. Pointing out a device’s perceived shortcomings is not an attack on the people that made it. One crucial role designers play (ideally) in product development is seeking out honest feedback, filtering it, and figuring out if that feedback can help make the product better for end users. The FOSS landscape needs a lot more of that.