I can easily come up with a simple set of polysurfaces that, when joined and offset, produce bizarre, counterintuitive results with offsetsrf (round or sharp edges). Apparently offsetsrf does not take into account the full range of edges that should be aligned.
It would be great to have a better offsetsrf. If not, another solution would be something that functions like a weld. One does the offsetsrf on individual surfaces then “welds” them together.
Another situation where such a comment might be useful is where following the plans creates a nonmanifold edge. Let’s say you have 4’x4’ rectangle with the corners filleted at 6". Now extrude that 3/8" to create a plate with rounded corners. Now the plans say to wrap a 3/4" bar around. If you do that with rhino you get a nonmanifold edge. But the weld command would fill in the gap between the bar and the plate.
I posted a file containing this one previously. With sharp corners the top center edges will not line up. With round corners the side edges to not line up.
This is just 4 planar surfaces at angles. Try an entire ship hull—good luck.