Health Disappearing After Refunding Items in Shop

This Is probably a visual bug but it says in all stats and such that I had lost health after refunding items. This occurred over 5 different games with different champions using different items.

After taking damage in lane and backing, I bought items as my health regenerated and then refunded the item(s) I bought and I lost x amount of health due to the refund. This was all done on the fountain of course. I found this frustrating when I would quickly buy and refund items early and rush to lane without looking at my health to see that I enter lane at half HP or so causing me to back early again or giving their jungler a free kill. I believe it works with any item but it seems has more effect on the more expensive items in the store. I tried it out in a custom game after taking damage from a tower as Blitzcrank and managed to proc my shield on the fountain after refunding items quick enough.

This probably isn't a massive bug or it might just be a random bug for me but it is rather frustrating when you have to get back to lane quickly.