How is it denial when we have records of sales data to back it up. It happened with Zelda 2 from Zelda 1 (3 million less) Majora's Mask from Ocarina of Time (4 million less). Spirit Tracks from Phantom Hourglass (1.7 million less).
It even happens with their other franchises.
Galaxy 2 sold around 4-5 million less than Galaxy 1 (HUGE drop). Handhelds that have 2 mainline Pokemon games usually follow the pattern of the 2nd ones selling less than the 1st ones (Gold/Silver sold 10 million less than Red/Blue; And Black/White sold 2 million less than Diamond/Pearl). Though, Sun/Moon looks to be the exception seeing as how that had Pokemon GO hype behind it + the series' 20th Anniversary.
If they were expecting gangbuster, 7-9 million numbers from Skyward Sword, now THAT'S delusional. And THAT'S being in denial. Because the game had many aspects going against it when it launched. So the fact that it STILL managed 4 million is a testament to the legacy, reception, and huge amount of respect that the Zelda franchise has accumulated throughout its lifespan.
With that said, I agree that if Breath of the Wild only managed to accumulate 4-5 million on two systems, that would be hugely dissappointing. Because it has a lot of momentum on its side.
Hardware Comparison Threads:
Current Thread
Is Hardware Getting TOO Powerful?
Older Threads:
PlayStation/Xbox/Switch: 2022 Edition
PlayStation/Xbox/Switch Hardware Battle: 2021 Edition!
PlayStation 4/Xbox One/Nintendo Switch: 2019 vs. 2020
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2017 vs. 2018
PlayStation 4: 2015 vs. 2016 vs. 2017