I’ve made a follow up to fix the issues experienced with the button appearing despite opting out of chat. The opposite scenario was also true (chat enabled but target user disabled chat). Both scenarios should now be fixed with this change:
https://github.com/discourse/discourse/pull/26237
The issue of the CSS still not updating for the button is a meta specific issue, we are using an older version of the user card theme component at the moment so the style changes aren’t reflected, but I will follow up on that and have it corrected soon.