I was so close to posting a complaint about the stamp shifting thing ruining my workflow- when I'm working with, for instance, layered materials, I shift them outside of the boundary to cut parts off before placing them, since placing them and deleting parts can sometimes cause issues.
But then I realised this is one of those cases, and it's probably doing more good than harm. I can think of just as many times where I have to piece half-stamps together since I can't properly shift them.
not sure if this is a bug: pipe removes deco of elements. Not related to the 93.0 beta, this also occures in the latest stable. Doesn't happen with portals, so I assume generally deco layer is stored in the particle.