I haven’t found it breaks my old saves for the unmodded original game, I can still load my saves up just fine.
How many developers guarantee backward compatability for save games based on user-installed 3rd party mods? I really don’t think it’s their obligation to offer support for modifications you make to your game, even if they provide (and improve) a system designed to facilitate it conveniently.
I would think it’d be almost a foregone conclusion that later patches will very often break compatility with older mods. That’s really up to the mod-makers themselves to support (or not). How would developers even attempt to maintain compatibility with modifications they didn’t write?