[Gameplay] When shop undo is used it undoes the life/mana gained since buying the item

Occasionally when I undo an item I bought I will lose all of the mana and hp gained while standing on the fountain since buying said item. Example. Playing Cait and recalled at low hp & mana. Bought dorans blade immediately upon recall. After 4 or 5 seconds press undo button and then buy something else and close shop. Both Hp & mana both still low despite being on the fountain for a good amount of time.

I have not tested this extensively but when I do notice it, it was right after using the undo.