They are just "not working properly if you keep them working while you're offline". So basically, you can place them in a World Anchor-ed area, but they will stop working, be damaged and such. (ask Gregfor more details).
I know that's not every single machine, but that's already a buff for guys not counting on Chunkloading to make them progress.
But not enough to counter "everything takes 10 times longer in SSP"
Edit: Suggestion: when you drop an item it should be unified.