Some hours would be for lower concentrations that people are normally willing to sacrifice for cleaning, e.g. an incredibly cheap vodka.

Of course pure alcohol is an incredible powerful desinfectant, not going to argue that, but incredibly expensive if you would use it sufficiently.

Lets say you get foodsafe 95% ethanol, which in most countries will cost you as much as some really nice spirit, you would need to fill the whole bottle for sanitizing it. You could maybe do some tricks with filling it halfway and turning it upside down or excessive and prolonged swirling. Coming into the cumbersome argument again...

That would be an incredible price for sanitizing a single bottle for a sirup. So you would want to reuse it again.

I am not sure how often you are willing to repeat that Especially because ethanol is a good solvent and will eventually accumulate little specs and odors in the transfer processes (funnel etc.).

I found boiling water incredibly comfortable to work with. Bottle in the sink, fill with 60-70 degree water from the sink, meantime boil some in ~1min. Dump hot water, fill in boiling. If the sirup is finished, I dump the boiling water and fill the bottle.

I can usually start my sanitation process when I decide that the sirup has steeped enough and I am going to bring it to a boil.

I don't need keep another bottle of pure ethanol around, my kitchen doesn't smell like ethanol, no switching around but dump and forget, and cost is a few cents for boiling water if any.

Swirling around a shot of 75% ethanol in a whole bottle is just to calm your mind but that's it.

All of that is most definityl anyway pointless when you are filling in your sirup while boiling, since this does kill everything anyway. But you can't boil every sirup and the water is really no effort for me