I see you have fallen victim to one of the classic blunders! The most common of these is "Never get involved in a land war in Asia", but only slightly less-well-known is this: "Never use the same name for multiple different potions when death is on the line!"
Personally, I always thought that it was not only deliberate, but clever, to have the Potions of Healing found in the Treasure Deck heal for a variable number of Body Points, since you never really know how useful any of the stuff you find in the dungeon is going to be. It contrasts nicely with the set-number Potions of Healing you find at specific locations in the Quest Notes, which presumably would have been prepared for a specific purpose.
To answer the thought more seriously: Hero Quest is a game that goes, if not all-in, that at least very far down the road that leads to simplicity, to the detriment of clarity - see also "Fire of Wrath", the "if a Hero reaches 0 Body Points" rules, or anything involving Mind Points, to name a few. It therefore seems fairly obvious that the game developers didn't feel like thumbing through the thesaurus to find four different ways of saying "potion" or "healing" - so they lumped all the potions that did the same thing into the same name. Thus all potions that heal are Potions of Healing... just with varying levels of effectiveness.
As for the fix: Exercise that vocabulary!
Here are just a few words that mean the same thing; I have attempted to order them from weakest to strongest (although I would take that claim with a grain of salt):
Mending
Alleviation
Wellness
Cure
Convalescence
Invigoration
Recovery
Restoration
Rejuvenation
Renewal
Or you can change the word describing the "class" of potion: Extracts are weaker than Tonics are weaker than Draughts are weaker than Potions are weaker than Elixirs, for example.
And there's also the classic D&D-style labeling: i.e. "Minor / Lesser / Major / Greater Potion of Healing".
(for the record, I use slev's "Hero Quest Revised" potion list - it includes all the potion types from the various expansions, plus a few extras to round out the set, and has the benefit of keeping all the various potion effects under distinct, easy-to-remember names (well, at least for me)).