I’d love to see your sources on that. Because all the definitions I’ve seen go further.
The shortest one relies on examples: https://cari.institute/aesthetics/cassette-futurism
The venerable and verborrhagic TVTropes: https://tvtropes.org/pmwiki/pmwiki.php/Main/CassetteFuturism
A fandom wiki: https://aesthetics.fandom.com/wiki/Cassette_Futurism
By your definition, Ferris Bueler’s day off is a cassette futurism movie. I don’t think even you agree with that.