LOL.. I will laugh also. I never said a tender boat is more seaworthy. You inferred it. I said that a stiff boat was not Steady. These are radically different concepts.
But its good that you pointed this out. Others may have also missed the point.
Well your logic seems not right to me. You said:
"... A steady ship on the contrary when exposed to the action of waves keeps nearly upright. the stiffest ships are the least steady."
.... the characteristics of a rough water boat is it reamains vertical in the presence of waves. This is the characteristic of the IP.
You have said that a rough water boat should remains vertical in the presence of waves, that a steady ship when exposed to the action of waves keeps nearly upright and that a stiffest ship are the least steady.
So by your words stiffness is prejudicial to a boat regarding to remain vertical when exposed to the action of the waves (steady). You say also that the characteristics of a rough water boat is to remain vertical in the presence of waves. Therefore, according to you, as the stiffness of a boat increases it decreases its capacity to stay vertical in the presence of waves and that is the characteristics that you say that make the boat a rough water boat. So a stiffer boat will be a worse rough water boat.
It seems clear that the main quality of a rough water boat is its seaworthiness.
I never said that the Oceanis is a tender boat I said that the 40class racer is massively more stiff and by your reasoning, since both boats share the same kind of hull, the Class40 should be less of a rough water boat (less seaworthy) than the Oceanis since the" stiffest ships are the least steady" and are, according to you ,the worst in what regards to stay vertical (steady) under the action of waves, the condition that you find more important to a rough water boat.
Acording with what you say, the Oceanis, that is a lot less stiff, should be a better rough water boat than the 40class racer. It is not, not even close, there is a huge difference. The Class40 is a true bluewater boat capable of sailing in high latitudes and really heavy weather and that is not the case with the Oceanis. Therefore all your reasoning is wrong.