In comments about his choices, Pivac said that while Anscombe was probably not back to 100 per cent fitness yet, his experience and ability to play at Test level was a factor in his decision.
Anscombe and another player returning from injury, flanker Ellis Jenkins, had done the job previously, and the selectors took that into account.
"We've had lengthy discussions on both those players, spoke to both before naming them but also their club coaches. There's been a bit of input from outside people, just to make sure we're not putting them out there when they're at risk. They'll be monitored accordingly.
"It's not our intention to play those players throughout the whole campaign," he said.
In Anscombe's case, that was because Pivac does not have England-based players for the All Blacks' Test as it is outside the international window.
Fellow first five-eighths Rhys Priestland is also selected. He hasn't played in Tests since 2017.
McNicholl is in because of his form and his ability to cover wing and fullback.
Pivac said he didn't think challenges in rugby came any greater than facing the All Blacks, especially when not being able to call on the England-based players.
"I want to comment that there's a lot of talk about why we're playing them at that time and if it lessens the occasion.
"The occasion, first and foremost, for these players and management is going to be huge. We've all missed playing in front of live crowds, and having a sell-out at the Principality Stadium is exciting for everyone involved.
"To have the best two teams in the world, the All Blacks and then the Springboks a week later, challenges don't get any bigger.
"If you're a player, I guess you're looking at it thinking there's a huge opportunity for me to perform on this stage and put myself in a good position for selection further down the track," he said.
Wales squad to face the All Blacks:
FORWARDS: Wyn Jones, Rhodri Jones, Rhys Carre, Ken Owens, Elliot Dee, Ryan Elias, Dillon Lewis, WillGriff John, Tomas Francis, Alun Wyn Jones, Adam Beard, Will Rowlands, Ben Carter, Seb Davies, Ross Moriarty, Taine Basham, Ellis Jenkins, Aaron Wainwright
BACKS: Tomos Williams, Gareth Davies, Kieran Hardy, Gareth Anscombe, Rhys Priestland, Johnny Williams, Jonathan Davies, Uilisi Halaholo, Ben Thomas, Josh Adams, Owen Lane, Johnny McNicholl, Liam Williams
The following players are in the full Autumn Series squad but unavailable to face the All Blacks: Louis Rees-Zammit, Nick Tompkins Dan Biggar, Callum Sheedy, Taulupe Faletau, Thomas Young and Christ Tshiunza.
The All Blacks face Wales at a sold-out Principality Stadium at 5.15am NZT on Sunday 31 October.