An analysis of KenPom data suggests otherwise. Of course that's why they play the games, but according to the KenPom ratings for that year, Duke would have been a strong favorite. Duke was far and away the best KenPom ranked team that year. The spread between them and the #2 team (UConn) was as large as the spread between #2 and #11 (UNC).
Here are all the KenPom spreads (post-championship game because that's what they list) for National Championship games and what the spread would have been if Duke had beaten UConn.
2021 - Gonzaga -2.61 Baylor
2019 - Virginia - 4.19 Texas Tech
2018 - Villanova - 9.56 Michigan
2017 - Gonzaga -3.83 UNC
2016 - Villanova - 2.19 UNC
2015 - Wisconsin - .24 Duke
2014 - Kentucky - .42 Connecticut
2013 - Louisville - 5.06 Michigan
2012 - Kentucky - 5.69 Kansas
2011 - Connecticut - 7.47 Butler
2010 - Duke - 10.74 Butler
2009 - UNC - 6.77 Michigan St.
2008 - Kansas - 3.70 Memphis
2007 - Florida - 1.48 Ohio St.
2006 - Florida - 4.88 UCLA
2005 - UNC -.09 Illinois
2004 - Duke - 7.64 Georgia Tech [???]
2003 - Kansas - 5.33 Syracuse
2002 - Maryland - 4.45 Indiana
I'm hoping I got all my math right because I did it quickly. A few interesting data points here:
If you count 2014 and 2015 as virtual KenPom pick 'ems, then only three real KenPom underdogs have won in the last 20 years. 2003 Syracuse, which was a big underdog (but not quite as big an underdog as Ga. Tech would have been), and Gonzaga 2021 and 2018.
Duke 2010 was the biggest favorite and came pretty close to losing, so of course it would have been possible to lose to Ga. Tech - again, that's why they play the games.
But, other than Kansas in 2003, every KenPom favorite of 4 points or more won the title. (9/10).
If you are a Gonzaga fan and look at this list it might make you feel worse than you already do.
In sum, based on this data (Duke being a 7.6 point KenPom favorite) you could argue that there was a better than 90% chance Duke would have won the title against Ga. Tech.