Why not make better use of CoW filesystems?

[BP25]

Hello everyone,
I'm planning to install Guix/Linux-libre with a CoW filesystem like 
BTRFS, hence the following question: would in this case not be neat to 
use the filesystem intrinsic snapshot feature for storing package 
generations, rather than using different folders (in the "current 
version" of the filesystem) as the Guix package manager seems to be 
doing?

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