It seems your documentation is updated again, so now it does take a single call with `properties` and `associations` again. But now this documentation is (in case of PHP) for the api-client v10, which is in beta, and there is no documentation to be found for v9…
So funny thing is, the v10 documentation works in v9, except the typehinting isn’t supporting it, meaning that PHPStan or similar tools are crying that we’re sending the wrong object..