The data migration might stem from the fact that the underlying data model is so totally different, that it just might not be possible to migrate anything. GA3

The data migration might stem from the fact that the underlying data model is so totally different, that it just might not be possible to migrate anything. GA3 and GA4 are so different, it isn't like the US and Russia, it is Earth and Jupiter (not in terms of impact or size, but just vastly different).