I'm 90% sure that this is not the case.
I believe that there is in fact a bug within alchemy whereby the strength of a potion is stuck at the value it was when that particular combination of ingredients was first combined to make that potion.
Example (sorry I can't actually remember what ingredients do what at this point):
Ingredient A and B both have Restore Health. Alchemy is at 40. Mixing them for the first time at that point result's in a potion that restores 22 health.
Once alchemy is at 70, mixing the same two ingredients will still only result in a potion that restores 22 health.
However if you then, Alchemy at 70 still, made a potion from ingredient A and C for the first time, still only for Restore Health, the strength of that particular potion mixture would then be capped at 73.
Note - Those figures are just arbitrary, I have no idea what the actual figures might be but the principle is the same.
My point is that potions don't scale, once you have mixed two, or more, ingredients together to get a particular effect the strength of that potion will then never change no matter how much higher your alchemy skill is. Which explains why people are getting potions with different strengths from different ingredients despite having the same potion effect and alchemy level.
Nope, sorry! I used the console to add every single Damage Health item and half of them I have never encountered or used but they still had the same magnitudes of ingredients I have used.

The majority of them follow a pattern, and this is independent of which items you have already used. There MIGHT be some form of glitch occuring, but it is definitely not the "stuck at same value" glitch from Oblivion. That is disproven by what I have done above.
*EDIT* ------
Oh and yeah, I am a huge Alchemy player and I have been monitoring my potions increasing in strength using the same ingredients. Just to doubly disprove your suggestion. *wink