Did any of the judges or examiners notice him using it through the 3 exams though?
You must be registered for see images
Examiner Lee, all 5 Kage and the entire crowd were watching. The mist triplets didn't notice what Boruto pulled on them even though they had him surrounded and up-close.
Shino, Tenten & their team had screens that were watching his battles and actively focusing on him. He does a fine job of hiding it. The chunnin exams OVA showed Naruto 'cheating' by accidentally activating Sage Mode against Konohamaru. The entire punchline and joke of that actual legit battle was that it was an unjust loss, that when rules are applied to deadly ninja combat.
Bottom line they are ninja, and the fact that only his own father was able to work it out means that I can't agree with you on this one bud. Even if it's lazy and unskilled to use, he's the victor as he would be in any actual situation. Naruto remains a hypocrite regardless due to the way he has cheated twice before and got his first ever jutsu by actually stealing an ancient relic.
The chunnin exams are to scout and promote strong and resourceful ninja even if they don't win their battle or use traditional tactics or earned power (Shikamaru was the lone Chunnin to rank up even though he wasn't the most 'skilled')