While I was working on T216888 I noticed that there isn't a good way to determine if a API module's parameters are valid before executing the module. I've added a crazy amount of logic just to deal with apierror-revisions-singlepage which can be seen here:
Provide a method to take in the parameter array and throw (or return) an error (if there is one). Then this method can be used during execution to validate the parameters. In essence, it's an abstraction of the validation code we already have.
Adding this method, would allow the MediaWiki-extensions-GraphQL to attempt to merge multiple requests, test the parameters, if they fail the validation, then we know the requests cannot be merged. This provides a quick way to check the merge-ability of requests.
Implement the logic in the MediaWiki-extensions-GraphQL (which is what we are doing now).
Alternatively, we could remove the request merging until this is resolved, but that is a significant performance regression.