So, the various sites say you're supposed to be able to set a chest as target, and indeed I get a minion response when right-clicking the staff on a chest from a distance. However, they don't put anything in there, and instead give me their loads in person as usual. This last time, though , they were digging a mineshaft, surface to level 9, and they had no ores for me at all, not even "in person".

Without version information i can't even tell you "works for me"

Version 1.11. Forge 2189 and 2199 both showed the behavior.