Are they three?
Can it be in proper English, things, or is it more correct to use “Are there three?” or “Are there three of them?”
Is it hypercorrection or some are more natural than the other ones?
The construction “We are [a number]”, referring to a group of people, is unusual but possible, as in Wordsworth’s poem ‘We are seven’ https://en.wikipedia.org/wiki/We_Are_Seven . I’ve never heard it used with inanimate objects.