API Management Services no longer logs query parameters set via inbound policies

Previously we used an stv1/standard APIM instance which had the following policy set on all APIs:

<policies>
  <inbound>
    <base />
    <set-query-parameter name="x-query-param" exists-action="override">
      <value>@(context.Request.Headers.GetValueOrDefault("x-header-name"))</value>
    </set-query-parameter>
...

When viewing logs within our Log Analytics workspace the BackendUrl property would contain this parameter tacked onto the end.

We recently created a brand new stv2/standard APIM instance with the SAME policy set. We now no longer receive x-query-param as a query parameter on the BackendUrl property as we would expect.

Why does this no longer work? Has there been a change to how policies function with an stv2/Standard instance?