At Lyndhurst Park, Wellington scored right on halftime to extend their advantage to 28-17, and Whanganui could not recover.
It is a strong home side that had dominated the Central Region U19/20 Shield, including against the Heartland Hurricanes.
"They've got a lot of talent down in that area," said Baldwin.
For Whanganui, Tyrone Albert scored two tries and kicked a conversion, while Phoenix Kairimu also dotted down.
Jack O'Leary scored his 32nd try of the season – 28 for St John's Whanganui Metro in the MRU Colts grade and four in the Development XV games – plus added a conversion.
This concluded the Development XV's much-disrupted campaign – they had only one week of training before the level 4 lockdowns, and planned games against Poverty Bay Turanga, Wellington Samoans, and Wairarapa Bush Maori were scrapped.
After level 2 saw training resume, they went 2-2 from their matches - beating previously scheduled King Country Development and new opponent Thames Valley Emerging Players, and then the losses to fellow new opponent Centurions and the rescheduled Wellington U19.
"The first two we had to win, the other two were always a bit tougher," said Baldwin.
"The guys can enjoy their off season, or be ready for the Heartland side."
Happenings
Cooks Gardens
Steelform Whanganui's game with Horowhenua Kapiti on Saturday will be open to the public, for a gold coin donation.
For Covid requirements, please keep a distance of 1m from other attendees, scan in with the NZ Tracer App, and avoid congregating at entrances or small spaces like bathrooms.
Face masks are encouraged.
Whanganui Women
An under-strength Whanganui Women's team did their best in Masterton in a 62-15 loss to Wairarapa Bush last Saturday.
With their Under 18 squad playing in Taupo, Whanganui had a very light bench and borrowed a couple of home players late in the piece.
Down 55-0, they scored three of the last four tries, including a length-of-the-field effort from fullback Shyna Tipu, and then hooker Kimberley Hunt grabbed a double.