Updates to darktable modules are designed to preserve old edits, though this cannot always be entirely guaranteed (due to the extent to which we can test all of the variations). I suspect that the comment from the other thread was referring to the fact that, at the time, the Pull Request was still a work in progress. By the time it was merged it will have been updated to handle old edits. Each module has its own internal version number allowing this sort of thing to be managed at a module level.
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