LineageOS definitely doesn't have most of the privacy and security of GrapheneOS. It lags significantly behind the standard Android Open Source Project (AOSP) updates which means not having all the standard patches and protections. Many of the patches aren't backported to older releases. It also doesn't use all the standard security features. LineageOS doesn't reduce privacy and security nearly as much as many of the operating systems based on it, but it's not as good as a production build of current AOSP on an up-to-date device. GrapheneOS makes massive improvements to the privacy and security of AOSP including providing many important protections missing in AOSP such as Contact Scopes, Storage Scopes and secure paste. It also fixes many privacy and security vulnerabilities not yet addressed in AOSP. They're not at all in the same space for privacy and security.
I think they are referring to that LineageOS by and large (there are probably exceptions) does not have support for relocking the bootloader. Some apps refuse to work with an unlocked bootloader (but there are ways around it).
It has drastically lower privacy and security. That includes apps getting far more data, VPN leaks, many serious privacy and security vulnerabilities being unpatched for many more months or years and not having greatly improved exploit protections mainly protected against apps and remote attacks. Protecting against data extraction is a small part of where security matters and there's much more to privacy than protecting against security vulnerabilities.
LineageOS definitely doesn't have most of the privacy and security of GrapheneOS. It lags significantly behind the standard Android Open Source Project (AOSP) updates which means not having all the standard patches and protections. Many of the patches aren't backported to older releases. It also doesn't use all the standard security features. LineageOS doesn't reduce privacy and security nearly as much as many of the operating systems based on it, but it's not as good as a production build of current AOSP on an up-to-date device. GrapheneOS makes massive improvements to the privacy and security of AOSP including providing many important protections missing in AOSP such as Contact Scopes, Storage Scopes and secure paste. It also fixes many privacy and security vulnerabilities not yet addressed in AOSP. They're not at all in the same space for privacy and security.
Actually LineageOS has less usability due to AOSP bugs, no GMS, unlocked boot loader, etc. The weak security is cost of wide support.
Could you explain how the ability to unlock a bootloader makes a device less usable?
I think they are referring to that LineageOS by and large (there are probably exceptions) does not have support for relocking the bootloader. Some apps refuse to work with an unlocked bootloader (but there are ways around it).
GrapheneOS has even less usability on my Oneplus 7T Pro, in fact it has none
i'm fine with that "less security" as my threat model does not include crossing the US border.
It has drastically lower privacy and security. That includes apps getting far more data, VPN leaks, many serious privacy and security vulnerabilities being unpatched for many more months or years and not having greatly improved exploit protections mainly protected against apps and remote attacks. Protecting against data extraction is a small part of where security matters and there's much more to privacy than protecting against security vulnerabilities.
You're conflating local data extraction with security vulnerabilities remotely exploitable via WhatsApp or RCE du jour. Don't.
GrapheneOS is significantly more private, secure, and usable than LineageOS.