Don't know how its achieved, but cold startup on my car with recommended no throttle has the idle revs hit 1300rpm briefly before settling on normal 1000rpm. The colder it is the longer the high idle but never more than a few seconds.

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone