I've been trying this out on my own local setup to test headless WordPress, and I found something similar, where the workaround provided in the other ticket didn't work for requests from the headless site, even though it appeared to work with the GraphQL IDE in the WordPress back end.
I tried a few alternatives and came up with this, which worked on my site, could you please check the same?
The intention is the same: if a GraphQL request passes the post slug then the WPML filters that normally handle returning posts in different languages are disabled.