Correct. For the sake of additional specificity, this is macOS 11.4 and Safari 14.1.1. I’m viewing meta in a private window and my own instance in a not-private window.
I must have botched my initial testing of Firefox, that works in the way you describe if the system preference for Use keyboard navigation to move focus between controls is enabled and tabs to a like button in the way I described previously if it is disabled.
I can reliably switch between behaviours by toggling that system preference without needing to reload the page in Firefox.
In Safari, I’m seeing it tab to a like button regardless of that system preference, even after reloading the page. I have not yet tested restarting Safari after enabling it.
I have now looked at Chrome as well, that works in the way you describe regardless of the system preference.