As you say, that wouldn't have made any difference since, if I understand you correctly, you thought/assumed that individual coins weighed 1.0g and 1.1g, rather than 10g and 11g. My wording was, I agree, a little potentially ambiguous."all the coins in 4 of the stacks weigh exactly 10g, but all of those in the fifth stack weigh 11g."
Another assumption I made was the figures of 10g & 11g applied to each individual coin on its own and not the total number of coins in the piles (10) although this matters not providing you make the same assumption apply to all piles therefore all piles weigh either 10g or 11g per coin or per stack of 10 coins.
Kind Regards, John.