I've been on calyxos and grapheneos since at least 11, and didn't realize they were gone from the google variant of android, since I've had them this entire time. I wonder, now, if it's an AOSP thing or a calyxos/grapheneos thing.
It's a LineageOS thing AFAIK. I'd be a bit surprised if GrapheneOS had it since they're quite close to stock AOSP when it comes to customisations that don't relate to security or privacy.