The only thing I can think of is when you wait the couple of seconds, the fuel lines get pressurized and maybe some extra fuel gets injected (causing puddling of fuel)while the servos/ injectorsare cycling and that makes the mixture too rich for a qicker start. If you press the button right away, the fuel is being sprayed (atomized) and it ignites easier for the instant start. It (harder starting)probably happens more when the bike is cold.Just my theory/ 2 cents.

 

That makes some sense speed.