Downvote is a positive action. It keeps inflation down.
Shadow Downvote makes zero sense. If you are the great 70+ guru, your downvote scares noone, the newbie gets a chance to learn from your wisdom.
Removing DV option from people under 70 might make sense if do not mind being condescending (proposing a number above your score makes no difference - the newcomer cannot look you up).
Nothing wrong with having frontends that do not show DVs but my guess is your friend has little too short attention span.