Right now English Wikipedia has a block like the following in its print.css added by @TheDJ :
.printfooter { clear: both; }
Originally, this looks to have been added to ensure that floating content at the bottom of the page before the print footer did not "fall out" and into the footer. Per some discussion, .mw-body-content has since the skin rework also had a float clear on ::after, but that functions only in @media screen, which misses the point for .printfooter.
An alternative to the title of the mentioned .mw-body-content::after block to something that always loads, whether in print or otherwise. I don't know where that would be.