SFMC Cloudpage Execution Context is always load

I am making a cloud page to be a subscription centre. When the page is requested with a GET I want the user to submit a form on the page. When the page is requested with a POST, I want to unsubscribe the user.

According to this page when a cloud page is requested with a get request, @@ExecCtx == "LOAD". When the page is requested with post request, @@ExecCtx == "POST".

However I can't seem to make this happen.

I made a cloud page that posts to itself:

%%[ VAR @key, @test SET @key = IsNullDefault(RequestParameter('key'), 'null') Set @action = CloudPagesURL(862, 'key', @key)]%%<form action="%%=Concat(@action)=%%" name="subscribeForm" method="POST">    ...<br>Context: %%=Concat(@@ExecCtx)=%%<br>Request Parameter 'key' : %%=Concat(@key)=%%<br>Listname: %%_listname%%<br>GET:  %%[[type="Get"]  Output(Now()) ]%%<br>POST: %%[[type="Post"] Output(Now()) ]%%</form>

However, even after submitting, and verifying that the request method is POST rather than GET, it seems to display only as a GET request?