If they were, I would raise it with my line manager and try to get the issue fed back to them.
What kind of workplace do you not trust your coleagues to be reasonable?
I don't trust myself nor anyone to not make mistakes or have blind-spots that pull requests and code review helps catch.
Here's an example from today of an issue caught code review, that could have been a bug that easily slipped through testing only to become a hard debug issue months or years later:
"You're assuming the order here, but it should be set explicitly".
Caught by the reviewer, and easily fixed in seconds.
But that could have been a really expensive bug to fix later.
And it wasn't really through a lack of competence, just an oversight because the data wasn't necessarily sorted at that point.
And the gating helps enforce and audit that code is reviewed, that everyone can go back and read the reviews to understand the journey the code went through. If there's later a bug in that area, there are now two different people I can know to ask first about that code.
Making code review optional is a good way to get it waved through with little oversight.
Having the people who okay the request share responsibility for fixing that code is a good way to motivate better code reviews as well as share knowledge.
Why would a coworker want to block your progress? Maybe I've never worked anywhere toxic enough to understand.