In my experience in the automotive field when trying to boost frozen cars, the conventional battery puts out the most power (at that temp) on initial draw. In other words, don't put any load on the battery to "try and warm it up". Everything goes down hill from there. We learnt to keep all accessories off, before trying to start a vehicle. If you could somehow warm the battery up with an external source such as a plug in battery blanket for an hour or more, then the battery was a lot more responsive and powerful being able to put out it's rated cranking amps. There is a big difference between cranking amps and cold cranking amps with a lead acid battery.
Lithium ion is almost the opposite. Put a load on the cold battery for a while, then try to start.
I'm guessing Maurice's bike starts better because by turning the ignition on??? then waiting before cranking, he is allowing the fuel pump to fully prime the bike before trying to start. Curious, what is the start procedure for these new Rockets since there is no key? How do you turn the ignition on? In the newer cars without keys, it's push the brake and start button together so no real way to "prime" the fuel system.