Having only ever driven manual gearboxes over 55 years of driving things like this are second nature to me. What I describe below of course applies to LHD cars such asthose driven in the US.
When, in neutral, you will find that there is a spring loaded action, requiring the US driver to pull left against a spring to enter the 1st/2nd gear plane otherwise the 3rd/4th plane would naturally be chosen.
Similarly, to enter the 5th/6th plane, the US driver needs to push the gear lever to the right, against a spring.Therefore it is obvious that when changing from 5th to 6th gear the US driver needs to keep pressure on the gear lever stick, to the right, otherwise it would naturally want to enter the 3rd/4th plane and you'd enter up in 4th gear.