That's quite the invalid assumption. Additionally, if I let Google run binaries on my system in one spot, it does not mean I have given them full access to run binaries elsewhere.
I suppose but when you're already using Chrome using the Widevine CDM isn't a huge difference. When you're using Edge using the PlayReady CDM isn't a huge difference.
I see the general theory of the argument for Opera and especially Firefox but even so, why trust a CDM blob less than any other commercial binary?