I asked for this awhile back as well, a lot of characters seem to only have the animation during home guards effect and not just a specific speed threshold. I.E. Homeguards brought me to this speed so through using ghost+everything else for movement speed I had hit the same speed.. alas no running animation. It really is a feel good moment.
A lot of times selling points for skins may include a new homeguard animation... which you only get to see after twenty minutes in summoner's rift. If the opposing team decides that they want to forfeit the game at twenty minutes you don't get to see it.
To be honest having the joy of seeing certain skins do things or have neat little animations keeps me in a good mood even if I am behind in lane.. it actually can help distract me from tilt and keep me focused on the game. I really hope that they look into this <3
Thank you so much for posting OP ! :)