The reason you see the effect in other places is because they’re not using tables but instead are using flex containers and you can do a lot more styling with them.
If you’ve never used flex, it’s really pretty easy and w3schools has (as usual) a good tutorial.
Also, (and I used this guys example as a starting point), check out this tutorial and go to the bottom and click on the “edit on codepen” link and then apply your .css to the column and see what you get. Aww heck… just hit that codepen and replace his .css with this:
border: 2px solid black;