Some of my experiences with the skill booster:
- Whether it does anything seems to be somewhat random.
- I have gotten previously unlearned skills with the skill boosters. Specifically, 2 points in writing or painting from the potent version, for sims who had never done any writing or painting. It seems more frequent for the sim to gain in a skill that they have already learned, however.
- There may be some latency involved - I have seen notifications with Charisma that the sim does not have the required relationships to progress, which makes sense for that skill. Then when the sim creates the additional relationships required, the skill boost shows up.
- I had a sim working on The Tinkerer LTW (max logic & handiness) - starting at logic 6, handiness 6.4 get 2 points handiness from a potent skill booster, then he drank several more with no apparent results. He then read the handy book to level 9.7, drank another potent skill booster which mastered handiness. I had him drink one more with logic at 6.0, and it mastered his logic and fulfilled the LTW. I don't know whether that single potent elixer actually gave him 4 levels of logic (from 6 to 10) or whether there was some latency in the previous ones he had consumed that all showed up at the same time.
Random mysteries are random and mysterious.