Um, there was only ever one flat-four Japanese bike, and that was the Honda Goldwing in 1000 (my old ride), 1100 and 1200ccs.
Those were anything but light on the front end. In fact, if you revved the GL1000 to redline and popped the clutch, the front end didn’t lunge skyward (even if you had the standard/non-tourer with no fairings) - all it did was light off the rear tire and leave a 150’ black streak on the pavement.
Do you perhaps mean the inline four bikes? I don’t remember my CB750 getting that light on the front end... but I suppose it helps if you’re not leaning all the way back and resting on the sissy bar at 120+. :P
I meant the inline 4’s like the Kawa Z-1, the Suzuki GS1100, and the Kawa 750 3 cylinder 2 cycle machine.