The Road & Track road test in April 1970 reports a top speed of 122 mph for the HLS30. Interestingly, the Road & Track introductory article on the Datsun 240Z shows the 5-speed as optional with a 3.70:1 final drive ratio. Indeed the 5-speed transmission was optional for the 2 liter roadster at the time.
Another issue I would like to take with the Petrolicious article is "S20 straight six in place of the normal car’s L24". The normal (Japanese home market with which the 432 is compared) car had a 2 liter straight six, not a 2.4 liter. In addition, reason number 3 is pure speculation. It would be possible to research that fact, but the writer didn't.