I reverted that change later and someone already commented on that a while ago I think and I elaborated on the reasoning but I can give you some more details.
Basically it comes down to this:
it is not possible, in a reliable way, to show only the cooldown of the item that was used. The client informs addons about changed cooldowns through an event which doesn't include any information about the specific cooldown that triggered it. Then the addon has to walk through all spells in the spellbook/items in the bags and request individual cooldown information for those spells/items which is indistinguishable for different potions after using one.
It is imaginable to implement a hacky workaround by hooking into various API functions that may activate cooldowns (usecontaineritem, castspellbyname etc.) but that would never be fully reliable as they don't notify you about whether a cooldown was actually started or not, and they may be called when a spell is not ready, during the casting of another spell etc. (Actually I may implement this at some point as an optional feature, but I hate hacky solutions)
The method I had implemented temporarily was one I saw used in cooline when I backported that a while ago (
http://forum.nostalrius.org/viewtopic.php?f=63&t=34628), which is to only show one cooldown for every unique start time. This is done by simply ignoring cooldowns with a start time that was already encountered before when walking through the bag items/spellbook after a cooldown update event. This meant only one potion cooldown was shown, but not necessarily for the potion that had been used. The reason I removed it again is twofold: it is clearly not a very elegant solution to the problem
and you can actually easily achieve the exact same effect using the ignore list. Just put all but one potion on the ignore list.