The Kiwi style kennels are second rate in design and user ease of use to the likes of a Mitton Hall kennel
cms4.ems-internet.co.uk
Your first post inferred that a benefit was that any pee and poo would fall through the slats which it actually doesn’t and you end up with pee and poo on the slats and the ground underneath, so double the cleaning.
I speak from the experience of a station I worked at where some dogs were in the kennels longer than others.
You can’t beat a nice bit of polished concrete that you can wash out and squeegee dry if you’re needing to clean up.