The problems this caused/s seems to have been an unintended / unforeseen consequence that was more exposed as people gained experience. There's a draft being worked on to officially change the priority:
> The behavior of ULA addressing as defined by [RFC6724] is preferred below legacy IPv4 addressing, thus rendering ULA IPv6 deployment functionally unusable in IPv4 / IPv6 dual-stacked environments. The lack of a consistent and supportable way to manipulate this behavior, across all platforms and at scale is counter to the operational behavior of GUA IPv6 addressing on nearly all modern operating systems that leverage a preference model based on [RFC6724].
* https://datatracker.ietf.org/doc/html/draft-ietf-v6ops-ula