Unlike the author, I do not think is a good idea. Elements are supposed to express semantics, but this just suggests behaviour. Not very descriptive behaviour either - since when does actual real-life toast smoothly rise and fall again? Possibly from the ceiling or coming in from the side? Why not just call it ? Or even better, don’t add anything - it’s surely just a that needs styling and animating with existing CSS…
Perhaps the inspiration came from the Sunbeam Radiant Control toaster:
Unlike modern toasters which rudely attempt to catapult your toast into orbit, the Sunbeam gracefully and almost silently presents your toast with the love and care it deserves.