User blog comment:PerhapsTheOtherOne/Speculative Spitballing: Goliath/@comment-173.58.100.7-20150608180157/@comment-25555436-20150608211530

Assuming Monty didn't have an actual idea of how big is 20 stories, it would explain why they don't look Kaiju size. Monty wanted to tell us they were very big, and the idea of them being "20 stories tall" came to his mind....even though he had no idea of how exactly big 20 stories actually are.

I think the term for this is "not drawn to scale" or something like that. They may be, canon-wise at least, 20 stories tall, but in the show they were definitely not drawn nor made that big, which leads to them looking smaller than they truly are.

If so, they wouldn't be the first. Many other things in fiction have suffered the same, too. Mostly due to technical limitations.

The other possibility is that everything in Remnant is just much smaller than in our world. I mean, for a society that is small and has only made things of their size all their life, what would be 20 stories tall for them may well be just 15cm for us, hypothetically speaking.