Cold spray and a hammer is faster and much less noisy and does not come with a free pyrotechnics display.

Because clearly, when stealing a bike, you want the entire neighborhood hear you for ten minutes, emitting sparks everywhere, while you had to bring an angle grinder.

You're supposed to be somewhat discreet when doing that, not warning everyone.

Most people's locks can be cut with a strong set of shears. The other ones are usually not worth spending your time on unless it's everything there is. In which case, like @jacquesm said, freezing temperatures are an excellent solution. More of a middle of the night thing though. Shears work 24/7.

Yeah I think the main benefit of using two locks is that a thief will just go for an easier option. IIRC similar rules apply to home security. It's not only about deterrence; making your house more of a nuisance than other houses is important too.

It does, but it requires power and time, and makes a ton of noise. Most thieves prefer something quick and quiet.

welp, if this entire thread taught me anything, is that I need to lojack (or whatever it's called) my bike.