I did the puzzle at lichess.org/training/xQc2e , and wanted to add the 'overloaded piece' theme. I was surprised to find it's not in the drop-down!
When searching on Google, the best explanation I found came here (lichess.org/forum/lichess-feedback/puzzles-v2-missing-overloading-theme-in-drop-down), where someone says overloading is either a synonym for deflection, or just a special case of deflection.
I don't entirely agree. Yes, you can argue that overloading does ultimately involve a deflection, but many deflection puzzles do not utilize overloading. The piece is guarding just one thing (not two), and oops, you can chase it away from the defense. To me there is information lost when you don't allow the tag of an overloaded piece specifically. For many puzzles, one tag is probably more relevant than the other. When the two are bundled, the tag seems... overloaded.
'Overloading' is also such a common and evocative name, that if they do insist on bundling the two, they should at least rename it to make it clear where overloading falls.