It does thought. You can't assign new meaning to $ and $$ and expect that it works flawlessly with magic statements and the stores.

At the very least the conversion between the versions will be very messy and error prones, especially using the migration tools.

Not to mention the designs of runes was still unstable back then. Heck even now it is still very awkward to use runes with sveltekit. You need $state and $effect everywhere for the page data.