I work on open source software on a team that doesn't handle any user data. [1] When people on other teams talk about data deletion they talk about having to make sure that when a user deletes something it really does get deleted from everywhere. I spent a couple minutes searching for a Google blog post explaining how this works and didn't find one, so rather than overpromise I just left it as "my impression".
[1] https://github.com/pagespeed/ngx_pagespeed