The argument that culturally homogeneous teams perform better due to more efficient communication (more is "already understood" at the outset, so there's less need to communicate explicitly, and fewer misunderstandings) is also sound.
So from a purely team-performance-maximising perspective, the question is: Which coefficient is higher? (More generally: What level of mixture is optimal?)
To a first approximation: whichever of the two your political leanings make you more comfortable with.
To a second approximation: if your task is efficiency at a constrained task, homogeneity. If your task requires exploration and/or creativity, heterogeneity.
To a third approximation: the 2nd approximation argument, except the demands of nearly all tasks change over time.
Then you factor in the environment, including your management's competence at eliciting the value of various team members, etc.
And don't forget risk. Optimizing for a high level of performance in any dimension makes things brittle in all other dimensions.
So, given a sound team culture and environment—great regardless of the style of team you have!—you can start with a diverse team and then collectively improve team cohesion and communication. You need some baseline level of effective leadership to do this, but it's absolutely doable, and I've seen it done.
But what fraction of that massively broader knowledge and experience is actually relevant to what the team works on? I think it will vary. It could be fairly high for UI design (as another commenter suggested), but low for, say, optimising backend APIs.
And do you really think it's easy to fix deep-seated communication issues? Do you think you could take someone from an Ask culture, and in a couple of weeks they'd be a happy, high-performing member of a Guess culture team (or vice versa)?
A team that develops a user interface benefits more from "generic" cultural diversity (gender, ethnicity, social class, etc.) than a team that builds a processor microarchitecture.
But the latter team can still benefit from diversity: if it's all EEs, they'll probably do worse than a team that also has a mathematician, a physicist, a chemical engineer, a finance person, etc on it.
On the other hand, the processor team's communication might be smoother with an all EE team of high "generic" diversity than it would be with all white guys but from very different academic backgrounds.
If you have decent retention, the team will develop its own communication style anyway, so I suspect this factor doesn't matter as much.
Did you just define Groupthink, but in positive sounding words?
False Equivalence.
Efficient Communication is secondary to Different Whats and Whys which is what a diverse collection of people from different cultural backgrounds bring to the table. A single idea communicated however imperfectly can change the world. This is the reason "equal opportunities" should be guaranteed to all even though "equal outcomes" cannot be guaranteed.
So define a "suitable standard requirement" for a specific role and try and collect a diverse group of people who meet those criteria.
Oh silly me, I thought the reason was that it follows naturally from everyone having equal moral worth.
I'm not claiming any "equivalence", only that performance is a function of (among other things) these two mutually exclusive things.
You can have efficient communication even in culturally/racially/whatever diverse teams. Your original implication that somehow only homogeneity leads to more efficient communication is not quite correct.