I do not agree. You should be able to tell from the sums whether it is a mimic or a regular chest. If in doubt, keep that chest until you levelled up. If the sum is below 11, it's a chest.
I agree with this -- the mimic is intended to be an inherently risky monster but with enough information (what's around it) you should be able to tell if its a safe chest or a mimic. It's intended to make you rethink the chest as a perpetually safe tile. It's most deceptive when you unveil it with no surrounding knowledge, that's for sure.