That they put in a preference for their own interests wouldn't be 'malicious intent' from their part, it would be 'why they built it in the first place'.
That said, it may be anti-competitive.
Unless contributions to add other search engines have been denied by the developers, it's not a strong argument.
Parts of the codebase are maintained by Intel, Nvidia, Microsoft and others. There have been times when Google engineers have had changes rejected by people from those companies.
You might be thinking of Android, which has a far less open governance...