Great question — answering as the UphillTech team:
The "nofollow" doesn't stop Google from actually indexing those pages. The only thing it does is making sure that Google Authority is not being sent to that page. The "noopener" does not have any effect on the indexing of the page. It's more of a security thing. Google says the following: Adding a rel="noopener" attribute prevents the new page from being able to access the window.opener property
Full answer by patrick: https://webmasters.stackexchange.com/a/123695 (CC BY-SA 4.0).
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