Why does my Fortify Restoration potion also improve Enchanting and Alchemy?

Solution 1:

The answer to your question is multi-faceted but most likely due to a mixture of UI decisions.

Easily found, is the Fandom Wikia regarding Skyrim potions. If you research this page you find that potions and ingredients have up to four effects. This is also experienced in playing when eating ingredients and learning one of its effects each time.

How this may be a UI decision is the space taken to display effects beyond secondary takes much visual real-estate wherefore many players want to get the basic info and move on.

Additionally, players who are interested in deep lore to include alchemic properties will likely take their own notes (The fandom Wikia lends credit to this in that it exists from player input and collected notes.)

There are at least four other first and second page search results on potions and what happens when, why, and how within Skyrim.

Please also note this is an answer to the main title and body question, not the OP self-answered theory.

Solution 2:

No, there isn't; it's just a bug related to how buff potions behave.