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You have a copyright on a song. If you create a second song you can call it a new "version" of the original or not, none of this matters for copyright.Well, some of it matters:
"If you pay close attention, you can hear it: there’s a new lushness in the opening banjo twangs, and an extra beat when she sings the lyric “Just say yes.” But the difference between the 2008 version of Taylor Swift’s “Love Story,” which helped propel Swift to pop stardom, and the 2021 rerelease of that same song is pretty subtle..."
"Her hope, it seems, is to override those archival works with these new versions..."
"What’s truly different about Swift’s “new” work is the intention behind it, and developments that have brought her to the place to own it."
https://time.com/5949979/why-taylor-swift-is-rerecording-old...
See also:
"In an interview with CBS’s Tracy Smith, Swift said that she planned to sidestep Braun by rerecording everything in the songbook that he now owns, meaning all the songs she had released prior to her August 2019 album Lover."
"When Swift switched over to Republic Records in the fall of 2018, she negotiated to own the master rights to all the music she creates going forward."
"By rerecording her old songbook with Republic Records, she will own the copyright to all of the new recordings."
https://www.vox.com/culture/22278732/taylor-swift-re-recordi...
TL;DR: Arguably, re-recording and re-publishing is just a new pull request and commit, but that gets you a new copyright.
But technically, it's the performance that has these financial rights, so perhaps this is more like a clean-room re-implementation so you can re-license the binary. :-)