If you postulate pre-Clovis settlements, now you need to explain why they weren't able to quickly expand to fill what was very fertile land for hunting, the way the Clovis people did. And how they managed to get so far south without having populations large enough to leave any unambiguous artifacts.
From the outside, I like Jared Diamond's article about it: https://www.edge.org/response-detail/27111
These "upending" discoveries of pre-Clovis sites remind me of the frequent news articles that were being written about the EM Drive which purported to revolutionize space travel by violating the fundamental law of conservation of momentum.