I wonder how they define "biggest opening over Independence Day" since the day off doesn't always fall on a weekend. The number they have for DotM ($115M) seems be the Friday-Monday number (where July 4 was a Monday), but it first released late Tuesday June 28 and doesn't include the numbers through Thursday. Another example, in 2012, Amazing Spider-Man was released on July 2/3, and the 4th was a Wednesday, so I dunno at what point you cut off the "opening" (as from release through first Sunday it had made $137M, over 6 days).
Looking at the big blockbuster releases closest to July 4:
2012: Amazing Spider-Man (July 4 was a Wednesday)
2013: Despicable Me 2 (July 4 was Thursday)
2014: Age of Extinction (July 4 was a Friday, but movie actually released the Friday prior)
2015: Terminator Genisys (July 4 was Saturday; this movie flopped and wasn't even top two on July 4, behind Jurassic World and Inside Out)
2016: The Legend of Tarzan / Purge Election Year (July 4 was a Monday! But also these movies bombed; Finding Dory was #1 on July 4)
2017: Despicable Me 3 (July 4 was Tuesday)
2018: Sicario 2 / The First Purge (July 4 was Wednesday; Ant-Man 2 released two days later)
2019: Spider-Man: Far From Home (July 4 was Thursday, the Thu-Sun number is $118M)
2020: lol covid
2021: Boss Baby 2 / Forever Purge (July 4 was Sunday; F9 made most money on July 4)
So yeah, only one weekend that similarly had a July 4 on Monday, and Tarzan was a big bomb.
And boy, July 4 really is the time for either Transformers, Minions or the Purge apparently.
