These are ABSOLUTELY NOT the reasons they changed /death. It was used to prevent things like trying to sneak your stone through the restless isles, or through barriers and such, as far as I can tell. These are exploits they have been trying to fix for some time and I guess they are trying yet another tactic.
Like you said, just about every major exploit you can imagine this would serve to address, it can be worked around by letting the environment kill you. Those 2 oozes at the entrance to the caves of the Restless Isles will be happy to perform a good-ole-fashioned /death on you.
So while I see how this could be used to close loopholes, I think it's much like the tools used to combat piracy (babababaaaa DRM). They serve to hurt more legitimate uses than they do illegitimate, for those that would undertake the latter route often are able to work around the limitation.