That is exactly my point. There is no reason to syntactically distinguish what is semantically non-distinguishable.

The interpretation of a request is up to the server. There is no reason for the client to syntactically distinguish that the request body is for a POST vs QUERY; the request parameters and response have the same shape with the same serialization format.

However, on the other side, a server does control interpretation, so it is responsible for documenting and enforcing how it will interpret. QUERY semantics vs generic POST semantics is a receive/server-side decision and thus should not be a syntactic element of client requests, merely a server description of endpoint semantics (“QUERY endpoint” meaning shorthand for POST endpoint with query semantics).

edit: Thinking about it some more, there is one possible semantic difference which is that a transparent caching layer could use a syntactically different POST (i.e. QUERY) to know it should be allowed to cache the request-response. I do not know enough about caching layers to know how exactly they make fill/eviction choices to know if that is important.