They're describing a bad experience with heavily using Android's user profiles for compartmentalization, not GrapheneOS. An incredibly tiny portion of what GrapheneOS provides has to do with user profiles. GrapheneOS does not restrict/limit users in the way they're describing. They're attributing a very niche way they chose to set up and use the device to GrapheneOS when it's not tied to it. See https://news.ycombinator.com/item?id=45244497.

Disabling Google Play apps as you're describing will heavily break other apps and will cause lots of issues. It will not reduce what they can do or access. It's not an alternative to the privacy or security features provided by GrapheneOS. What the person above is describing has little to do with GrapheneOS specifically and doesn't make sense as an approach to using it.

Recommend reading https://grapheneos.org/features and looking at https://eylenburg.github.io/android_comparison.htm for an understanding of what GrapheneOS provides.