I think it's fine. 4xx is a way of saying the client did something wrong that it can potentially fix (i.e. slow down requests). 5xx is more opaque meaning there is nothing the client can do to fix the problem.

In general 4xx errors are problems with the request, and 5xx errors are operational issues with the server/network

Too continue. It's "you're sending ttoo many requests" not "server is overloaded/getting too many requests". Hence it's a client error 4xx, and not server 5xx.

Put that way, it makes sense. Thanks.