In the case of the video it's just an old type of governor. Because at startup the RPM is not at the set value, the engine gets maximum injection and because it's not yet at speed, the air/fuel mixture is incredibly rich causing the smoke.
This can be prevented with basic electronically controlled injection systems, which don't just put fuel to 100% on startup.
A similar situation happens when you have a turbodiesel that you suddenly load up. First the governor opens, and only after the turbo spools up, you'll have a good air/fuel ratio again, and the smoke fully disappears.
Petrol engines should never smoke. If they do, they're burning oil. During starting you definitely get exhaust gases coming out of the tailpipe but no smoke. Water vapor can very much be exhausted, if it's quite humid and cold. but that often goes away within 10 minutes or so.