Hakaraia, who is well regarded for not tolerating foul play within his Ruapehu senior team, was shocked at the first yellow card of his career.
"[The official] apologised but had actually gone on and made it," said Munro.
The team made do, as Kaierau winger Stuart Brosnahan had moved into openside flanker for the match and had a good game.
Munro said powerful midfielder Kameli Kuruyabaki was probably the difference between the two sides.
"If you had to name one, because they all stood up, he was bloody outstanding."
Wairarapa-Bush came back at Wanganui twice in the latter stages, but they held on to the crown they won as an Under-19 team in 2014, along with 2013 when the team was again the Wanganui U20s.
The Wanganui U18s had a grind against Taranaki Secondary Schools in Hawera, losing a tight match 8-0.
Wanganui's defence held out against an early onslaught, with the tight five putting in a big effort in and around the ruck.
Junior Ainea had a standout game putting in some hard tackles and turning over possession at the breakdown.
Daniel Kauika had another solid game at fullback and made good breaks out wide.
Taranaki got a penalty in front of the posts to lead 3-0 at halftime, and while Wanganui kept defending hard, Taranaki eventually got through as their winger went over in the corner.
Having given a lot to hold the home team out, Wanganui had few chances on attack and were shut down at each stage.
Coaches Cornel Mason and Daniel Tamehana have a good idea on their work-on's before their HYRC Cup campaign starts against Wellington at Cooks Gardens this Saturday.
The Wanganui U16s were desperately unlucky in their 22-19 loss to Manawatu U16s at Spriggens Park. The home team led for most of the game before giving up an unconverted try with time up on the clock.