I'm not an expert on this, but I have a different take. I think that "is" happens when there is an implicit gerund before the plural noun.

- [Working] five days in the office is too much (I do think that the title should be "too much", not "too many")

- [Having] two hundred students is better than [having] none.

That is, there is an implicit subject, and it is not the plural noun, which is actually a direct object.