When you have a lot of cubs, it's easier to just mash the same button a dozen or two times, rather than going to a dropdown box each time you want to select a new cub before hitting the button, or making sure you put all of your cubs into the first cave that gets listed in the dropdown.

(For some RP reasons, I can see why some people will want to have their cubs in a cave with their mum, etc, but they could still do that without it needing to affect training, since cub training flavour text is all about your main male.)

It would be nice if cub training was just unaffected by the caves and all available cubs were listed like they had been before.