How to get <Grid> items to stretch the entire height of the Grid?

[vital moss]

The <Grid align='stretch'> documentation is a bit misleading. The documentation shows the grid items stretching their height, but if you look closely they only stretch to the tallest item in their row.

Do any flex-experts here know how to get the items to actually stretch to the entire height of the Grid? I've been trying in this sandbox with no luck:

https://codesandbox.io/s/practical-pateu-nzjrgm?file=/src/Demo.tsx

Update: I found why Mantine's Grid is behaving like this. It's because it wraps its children with an 'inner' div which doesn't fill the parent Grid. @remote shard do you know why?