I remember my brother doing the same thing about 10 years ago. When I ask about why he manually cast one obsidian he is not sure if its a visual bug but he feel it heal faster, I never believe him.
I think this is an oversight on Blizzard's part when they designed Obsidian Statues; whoever programmed the statues didn't think to make the healing buff duration == heal spell cooldown. However, I think their intent was to make it so one unit could only be healed by one healer at a time. It's not really a bug because the game is working correctly, but I suspect that it was completely unintended. This could be "fixed" by making those two timers equal to each other, but I don't think it needs to be.
The game logic is pretty simple: If targeted unit DOESN'T have the buff then apply the heal. These buffs (the little icon) have a set duration, for the Priest's heal they made the duration the same as the spell's cooldown. For the Statue's heal they made the buff duration shorter than the cooldown. I'd have to say it's not a bug as the mechanics are working as intended and it's safe to assume that the devs wanted to allow multiple statues to benefit the same unit if their casts were offset enough.
if you dig deeper you will find that icon lasts 1s after heal from priest and 1s after heal from statue difference is value Animation Cast Point which is 0.5s for priest it is his spell animation (time it takes to cast a spell) as for many spells for some other spells this value is ignored but for statue there is no cast animation, but Animation Cast Point is not ignored, it is just added to cooldown, this is very unusual
i love how Blizzard's RTS games have lots of these "tryhard" moments which would give you an edge if you don't mind clicking more e.g. in Starcraft 1 when you hit&run your ranged units target enemies quicker if you rightclick enemy unit than A+move near it
That is a pretty big deal if your whole army needs to be healed quicker but because of all the extra APM needed and you have to focus on that instead of something else I don't mind it too much as a game mechanic.
Pretty sure this has always been a thing. Undead is not my main but I've always used the statues like this while in my base to super fast heal up my army and go again, I do think it's pretty imba but I like it being in the game.
I thought it's a well known trick cuz every UD pro back in 00s was doing it. Mostly to get both mana and hp regen at the same time while having only one statue.
wait... so when i have more than one statue on healing, it isnt actually doing anything? how did i never notice that i was playing this game for over 16 years!