your reasoning is very basic, but wrong.
The 4-stroke duct length is highly depending on valve timing. There is no such input in the sample you provided. Tame engines need short ducts, hot engines need quite a bit of pipe length.
Then again, the two stroke timing is depending on intake timing, both in duration as in port area, which is called the time-area factor.
Just assuming that the time is half the time in a 4-stroke is true for cycle duration only, and has no bearing at all on gas exchange capacity for a single two stroke port.