As you said in the article, participating in code reviews is an opportunity for growth in countless ways. Junior developers should feel encouraged to partake and positively impact the team.
Please instead flag things you don't understand and ask for an explanation. It's worth a senior developer's time to think about it, and either provide some useful training, or more often than they might be comfortable with, ask themselves some hard questions. Your fresh "junior" eyes are a feature as often as a bug, and see things that the seniors don't anymore.
I'd much rather have a junior give me a code review with, uh, less sophisticated criticisms, than one that assumes I know what I'm doing. It's at least a sign that they have paid attention.
But ultimately, it can be a team rule to require every developer to spend some time on code review each day. I worked in some teams where you needed to review PRs to get review on your own. It worked pretty well :)