Items with regen % does not stack

Hi Lakoo, Just came to know to my horror that items that gives % regen to HP&MP does not stack. For example, if I have a revival sword that gives 20% regen stats and a phoenix from the ash ring that gives 5% regen stats, the total regen after battle that I will receive will only be 20% (the higher of all in your regen items) instead of 25%. I don't understand why is this so since the game provided regen % items on ring, weapon, fashion, helm, etc etc. Can Lakoo please advice? Thanks Sam