| Loz
As you know, a tire that is inflated to a lower pressure than recommended will have a tire profile that will sag slightly in the middle. This sagging profile results in increased rolling friction and causes the tires to run hotter. This will reduce tire life but it will also increase tire traction or grip. Depending upon racing conditions and the overall setup of the bike the increased grip may be necessary to be competitive even at the cost of tire life.
A tire manufacturer will recommend a pressure that is a balance between tire life and grip. When a bike manufacturer is developing a new model their test riders will determine what pressures in their opinion, best suit the new model. The recommended pressures are the best for general street (not track) riding, so you can increase grip somewhat by reducing pressures.
But to answer your question about higher recommended tire pressures for Japanese in-line fours versus Ducati twins - in-line fours heat up their tires more than a twin so a higher starting pressure is needed to prevent overheating the tires, particularly the rear tire.
Years ago, superbike racers discovered that it was easier to modulate the power to prevent wheelspin on the Ducati V-twins than it was to do the same on the Japanese inline-fours. This is because there is a longer interval (in terms of both time and crankshaft rotation) between cylinders firing, which gives the rear tire a "break" - time to recover traction and match its speed to that of the motorcycle.
More recently, more sophisticated traction control systems have been tried to reduce tire temperatures, improve tire life and lap times.  | 
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