I get the intent, but I’m not sure this really buys much. If a package is compromised, the whole thing is already untrustworthy and skipping postinstall doesn’t suddenly make the rest of the code safe. If it isn’t compromised, then you risk breaking legitimate installation steps.
From a security perspective, it feels like an odd tradeoff. I don’t have hard data, but I’d wager we see far more vulnerabilities patched through regular updates than actual supply-chain compromises. Delaying or blocking updates in general tends to increase your exposure rather than reduce it.