Hi @dram
Looks like we did make a recent update here.
We recently shipped a designer tweak to autoinflate empty columns or tracks that are fr with a 75px minimum — similar to how a div has a base height when first added to the canvas. This is an added convenience so that you can drag elements into the cell. Without this, the columns or rows may collapse and cause an even more annoying issue with adding content.
If you turn off the “grid lines” (hide/empty lines button in the left sidebar), it should “turn off” the inflator here and those empty columns will collapse.
Hope this helps provide some clarification!