And the Piaggio P-180 Avanti II manual says...
Mmo 0.7
Unless you prefer to second-guess certification test pilots findings, without reasons or arguments, concern is unjustified.
Strength, direction and speed at which mach effects occur is generally related to wing shape, both profile and planform. Saying that Ma 0.70 must be close to mach tuck is rather uninformed, as is responding that the plane doesn't mach tuck because it's canard .