Monday, 16th May 2016, 15:18 by milski
I'm not the OP, but:
All other effects on the wand of random uselessness attempt to affect an enemy target (though there are a couple buffs). Having digging on random uselessness is tedious, spoilery (you may not realize it can dig for many runs), and encourages inventory clutter. It also makes digging much more common (if unreliable) early on since digging wands seem to be rarer than random uselessness. By removing digging we can (slightly) focus the wand of random effects as an offensive wand, (slightly) make digging rarer and more intuitive, and unspoiler the wand.
I'm not fully sold on that argument, but I'd imagine if we were designing a random uselessness wand from scratch, it would likely not have digging on it for those reasons.
E: As for that specific situation, for argument's sake you could say it's just an example of how you can use tedious, spoilery behavior with wands of random effects in order to ninja areas. The fact the player needed two spoilery bits of information (random effects can dig, how the vault was designed) is kind of irrelevant.