It seems that there are some CSS settings inherited by the editor. In general (like here https://handsontable.com/docs/9.0.1/demo-scrolling.html) editor takes the width of the column (or more if there’s more content).
I recommend inspecting it on the CSS tab in the Chrome dev tools.
Actually, there is a flexbox. We tried adding this piece of css just to override the size of the text editor, although it doesn’t automatically adjust based on the cell size but we’ll see if this is acceptable.
Also, I’ve found something that solves this issue without removing the ‘display: flex’ in the body. We’ve added this line of code as workaround.