Contrary to belief.
Unless manufactures use a thicker wall in the 30mm tube over a 25mm tube, the UTS (Ultimate Tensile Strength) and Tensileelongation between the 2 will be very very close,when it comes to soft core tubes and hybrid tubes.
The only thing that makes tubes stronger is the material its made from , and the process its made by.
The whole point of a 30mm tube is to get more moa so the wall thicknesses should be the same weather the over all diameter is 25mm or 30mm or now the 34mm.
The exception will be like examples such as the Leupold. They probably have to use a thicker walled tube, especially if they use the same "internal guts" as they do on the 25mm tube.This is because it would give a more secure internal fit
so the gutts don't slop around.
In cases like this, the tube will be stronger because the tube wall thickness would be thicker.