I had the same experience with 10mg/day SR micronized pharma compounded Preg.
Libido shot up to above 16yo me levels, I had to masturbate 6-7 times/day + sex with my girlfriend or I would lose my mind.
I doubt very much it was placebo because I wasn't thinking about sex drive at all when I took the Preg, I had no idea it could have that effect, I was only focused on verbal fluency, mood, etc...
It did help those things to some extent, but the highest impact was definitely libido; completely ridiculous. It calmed down a bit but even after a couple months on it my baseline was a lot higher than pre-Preg.
Full disclaimer though, I've always had a much higher sex drive than average so this won't necessarily happen to someone else. Even on my worst protocols and in the midst of suicidal depression pre-TRT with 6ng/dL Free T, my libido was really high and dick working great.
I wish I'd gotten as lucky when it comes to neurotransmitter action and my reward system