Sloppy scholarship. On the other hand, it's simply a credit attribution of posing the problem, so it's not material in evaluating the results. I observe that the majority of references I can find that attribute this to Tutte are very indirect - i.e., citing sources that themselves claim Tutte was one of the people who formulated it - so it would take someone with a little more time on their hands (or perhaps an LLM) to track down the original...
Not necessarily. Double entry bookkeeping catches errors in cases where an amount posted to one account does not have an equally offsetting post in another account or accounts (i.e., it catches errors when the books do not balance). It would not on its own catch errors where the original posted amount is incorrect due to a mistaken assumption, or if the offset balances but is allocated incorrectly.
You probably know this but, for anyone else who is interested, the easiest way to get a feel for Icon nowadays may be through its descendant Unicon which is available at unicon.org.
