By your reasoning, simple breach of a civil contract means jail time. That just isn’t so, except when it comes to the IRS.
He might get it sooner or later. :)
False, misleading or otherwise fraudulent statements, or knowingly withholding the payment of taxes on income, if substantial, constitutes criminal activity.
Almost all mistakes on a tax return are civil matters and are handled by interest and civil penalties. So whether you like the IRS or not, and most don't, one cannot simply "fall" into a criminal trap.