The 5% being decided by a judge seems low, but maybe not so much. If about 15 to 20% go to court over custody, many of those eventually end in a settlement in mediation or otherwise. Sometimes an attorney sees that the judge isn't buying her/his party's arguments and they may look for an agreement. In those cases, it can be correctly stated that a judge did not decide it. Rarely does it come down to a sudden surprise decision.
Whatever the true statistics, they can be easily misunderstood. I would hardly say that 95% of NCP's are happy to be NCP's, but some people will say that the fact that so few are decided by a judge means that fathers don't have custody because they don't want it. Though we all know that is usually BS, you can't really disprove it.
Futhermore it makes it hard to argue that fathers are unfairly treated in court based on the percentages of NCP Dads. You would need to get the male-female percentages on that last 5%, but that information is unattainable. The most reliable information is derived from child support statistics, which gives us the percentage of fathers and mothers who are CP's who receive child support.
Everything else is general perception. It may be true that fathers are cheated in custody court, but good luck proving it by the statistics.