Got an update. It turns out other browsers are not implementing HTML lists using CSS, that's why when using the CSS property `all` it still works.
It's not a #Firefox #bug because the `all` property did reset the `counter-reset` property as per the CSS spec, and it is in Firefox's default UA stylesheet.
To quote Emilio Cobos Álvarez (https://bugzilla.mozilla.org/show_bug.cgi?id=1881517#c4):
> Yeah, this is not really a regression from that change, and this is really invalid. Firefox implements CSS lists using CSS counters as per spec, so you're really resetting https://searchfox.org/mozilla-central/rev/a8cc31504a2379bcf8ba395d2da7bb632b5521d6/layout/style/res/html.css#570.
>
> The issue is that other browsers don't implement html lists using CSS.
In other words, if you are using the modern way to do a #reset:
```
* {
all: unset;
display: revert;
}
```
You also have to re-add `counter-reset: list-item` to `ol` like so:
```
ol { counter-reset: list-item; }
```
This is why I love Firefox, they stick to the #W3C specs. You learn in the process.