This proposal seems like a powerful subsidy for Microsoft and OpenAI. Why can they partner while Google and Anthropic can't? It is strange to penalize a non-monopoly partnership like this.
As an extreme example, Oracle had a dominant position in the enterprise database market in the late '90s, but it wouldn't have been an abuse of that position if they'd integrated a web browser into Oracle 8.
Breaking one will absolutely give the other an unfair advantage and entrench a market leader, which is against the principles of antitrust.