The $30 first-party cases are not appreciated by the users of the Pixel 6 and 6 Pro. There are dozens of people complaining about the transparent plastic showing extreme yellowing, warping, or just not fitting the phone from the factory, looking at the reviews on Amazon. Some users have posted pictures of their cases, saying that they degraded in a few months. The case has started to look a bit dingy according to an editor at The Verge.
There are a lot of positive reviews for the cases, but it's hard to ignore the number of complaints. It's not likely that this is from a bad bunch of cases. There is a thread complaining about the issue from January and one with almost the exact same complaints from a few hours ago. The cases start to change shape around the buttons, which would make me worry about its ability to protect my phone. The Verge asked for comment on whether these were known issues.
This kind of rapid discoloration is familiar to anyone who has bought a $10 translucent phone case. It is a fact of life with translucent plastic. Even a lot of the negative reviews admit that they expected the discoloration to happen at some point, but they didn't expect it to look so gross when it happened. I don't think I've seen it this bad before.
Again, though, this isn't some bargain, no-name case; it's one sold and branded by the same company that makes the phones. This is a problem that has been solved in the past. A few of my colleagues had fond memories of the fabric cases the company made for phones, as did a few commenters, though there were also a fair amount of complaints. If they got dirty, you could clean them off easily.
Thankfully, there are plenty of third-party cases these days, but it is a bit disappointing that getting the official one is such a gamble. It's best to steer clear of these reports unless the company announces that it has fixed the issue, and if the cases for the more budget-conscious phone are similar.