Yeah I've been getting this same issue since around september on my Pixel 8 Pro and seems to still be present now.
It doesn't act consistently, sometimes the limit activates even when it didnt on a previous boot and hadn't charged it to full with the shield up, but then the next time the limit won't activate.
Charging to full until the shield shows doesn't help, because one or two charges later it will try to charge to 100% again.
But issue might be linked to reboots.
EDIT: NVM it's an upstream issue, but is linked to reboots. https://github.com/GrapheneOS/os-issue-tracker/issues/6123#issuecomment-3394739478