On: Firefox 81.0

[boomboomsubban]

I'd guess primarily language, the status page says their testing to ensure the right fields get filled.

[andybak → boomboomsubban]

We speak a kind of English over here in the UK too.

[boomboomsubban → andybak]

There are enough differences that could cause issues in form recognition, particularly with things like addresses, that it makes sense to separate the two for testing.

[gpm → boomboomsubban]

Canada is about as similar to the UK as it is to the US in this regard.