Just because people continue to claim it so on the forum does not make it so. The functionality within the YouTube channel on Roku devices is under 100% control of Google. There is absolutely nothing Roku could possibly do to block access to something within a 3rd party channel. Every person that reported the problem, then discovered they didn't have their birth year entered into their Google account and added the year, could then view the age-restricted material.
For your scenario to be correct, Roku would have to be able to monitor the content within another company's channel, and then block said content. That is impossible. The channel developers (in this case Google) have the only control of the coding within the channel.
Google is the one that flags their content as age restricted. There's no way an outside company could monitor that content and determine if it should be age restricted. Especially if it hadn't even begun streaming yet.
It doesn't matter if YouTube works differently on different devices. Not the same app in the slightest. It's written in a different programming language and the code cannot be used on a different device. If there's a difference in functionality between the same app on different devices, that's the programmer's doing, not the platform provider.
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