> Manchester City is a team with a long history.
> Manchester City are lined up on the field.
The count/mass noun issue comes into play when one is counting the thing in question, in which case corporations are clearly count nouns. E.g. you'd refer to several new Facebook-like corporations as "a new crop of Facebooks", not "..of Facebook".
But Facebook as a company is plural: "Facebook are certain that metaverse is going to be big". This is because a company cannot think and be certain, so the full form is actually "Folks at Facebook are certain that metaverse is going to be big", and it makes perfect grammatical sense.
Why is "folks" the right way to think about that? Why is it not "Mark (Zuckerberg) (at Facebook) is certain..."?
Incidentally, I think it's funny (but justifiable) that you used "is" here:
> But Facebook as a company is plural
This sounds natural to me.
Notice “skate” versus “skates” in these cases:
- Alice skates; Alice is a skater.
- Alice and Bob skate; Alice and Bob are skaters.
- She skates; she is a skater.
- You skate; you are a skater.
- You skate; you are skaters.
- They skate; they are a skater.
- They skate; they are skaters.