Created attachment 459118 [details]
screenshot of the bug and examples of how it should behave

This behaviour is only in Safari 15.4. Everything works as expected in 15.3 and earlier.

A grid container with an `aspect-ratio` and a width of `auto` or a percentage will not allow its children to use the available space.
If the width is a fixed value (with `px`, `rem`, etc.) or if it is set in viewport units, it behaves as expected.

In the attached screenshot, all three should look the same. 
The element with the text has an `align-self: end` which should move it to the bottom of the parent. It does for the examples using `px` and `vw` widths, but not the one using `%`.

You can also see a live example of this here: https://cdpn.io/pen/debug/MWQyMOV