In flight, the engines are at Flight Idle, i.e. partially spooled up and advance to full Go Around Thrust is very rapid.
As the post mentions that the aircraft had already touched down, the engines would be in Ground Idle, requiring a considerably longer time to spool up to Go Around thrust.
That may account for the apparent length of time before you perceived the engines to be set to Go Around thrust.
Regards,
Old Smokey