Privacy is not a super-set of Open Source. They're two different things; somewhat correlated, but only insomuch as the auditability and self-correction of any claims to privacy may be.
Auditability is important, but most people won't do it, and even those who do miss things; OpenSSL is fully auditable, yet security bugs are discovered every year. Its not the same thing, but its in the same vein; just becuase we're capable of catching a needle among the haystack of a million lines of code doesn't mean we will (in the case of the MOTD, its less of a needle and more of a giagantic pile of crap just laying on top).
Self-Correction is important, but even fewer people will do it. Defaults Matter. People just don't dive into VSCode and rip out Microsoft's analytics tracking code en mass. It doesn't happen. People use the defaults.
In the face of these two assertions; Open Source is important in the fight for Privacy, there's no doubt about that. But even more important than that is Trust. Its not enough to see the code; its important that the organization and people writing it have a demonstrated history of caring about the privacy of their users, and that they've taken both "table-stakes" and "above and beyond" steps to assert their position on the matter on behalf of those users.
Canonical does not have this demonstrated history. They barely lurch in the right direction, against their collective wills, when we care enough to crusade across the internet to convince them that they're wrong. By comparison; Apple does care. You can complain that its in the interest of their profit margins (OF COURSE IT IS) or that its genuine (I'd bet my net worth that this is also true); it doesn't matter. They productized full disk encryption with hardware security modules. They don't just support hardware MFA; they make it the default. When they realized phones wouldn't have the power to do natural-language processing on voice in the same way servers do, they didn't just throw their hands up and move everything to the server like Google did; they made better silicon. That's their history; Canonical's history is sending keystrokes to Amazon so they can sell you more expensive toilet paper. The most knowledgeable Ubuntu users turn this off; the most vulnerable won't even know its happening.
Everyone is welcome to their own opinion on this, and you're also welcome to place the value of open source above the value of privacy; but I take the stance that Privacy isn't negotiable, and its more important than a product being open source or having privacy if you tweak the knobs in just the right way.