When dealing with custom machined assemblies, especally those using a press fit instead of a standard thread for the nut, getting the component off without damage can be a headache. This is definately a clever way to secure a heavy pin, but it requires a bit of technique to disassemble.
I found that just trying to yank the nut off often doesn't work because the friction is far too high. The best trick is ussually to try and rotate the nut into a specific upper position. You need to get the nut to sit as high as posible on the shaft or pin, which reduces the friction profile significantly. Once it's seated up there, a strong, steady rotation with leverage shoud break the seal and allow it to come apart. If the piece is large, you might need to introduce a thin, non-marring spacer just to create that neccesary clearance for the rotation. It's all about managing that contact area and utilizing mechanics rather than brute force. It’s a neat little trick for DIY mechanical work.