This is just a client router cache issue.. so basically as op mentioned it works with server actions but not route handlers. This is because a server action handles both the actual work and the revalidation in the same request. With a route handlers you need to manually add a router.refresh() to reload the page and actually get the fresh data. Nextjs 15 adds a way for you to completely disable this cache but idt that exists for 14.

Answered the same in the reddit post