We've had two reported issues in Kibana that column widths aren't being calculated properly when initialWidth is not in use. They don't "expand" to fill the width given the width available. I think this is due to the various hooks being called before the grid is painted on the page. Likely we need a slight pause before the widths are calculated so the main wrapping grid can grow to fill the container before the calculation is made.

I've double checked this is not a CSS issue, and although there's likely something that can be done downstream to force some of these widths, it's likely smart to do some checks in EUI to make it more reliable. Alternatively, we could do a check to see if the width of the grid changes size and make calculations then.