You generally can’t contact users who are exclusively buyers here, their profiles lack the Contact button, which is to protect them from all the spam they would get else.
And you aren’t supposed to contact sellers (who sometimes are buyers too but have the contact button because they are sellers) either, unless it’s to buy a gig or ask questions because you intend to buy from them.
Seller profiles do have a contact button, and we do get a lot of spam even though spamming isn’t allowed.
While I understand your wish to talk to one of the reviewers - as someone who has been contacted and asked about a gig/seller I bought from, I can tell you that I did not like it and I’m glad that it happened only once yet.
For one, being a seller and having that contact option on my profile, I do get a lot of spam that eats into my time already (sellers have to react to everything including spam and scam messages because of metrics like response rate and time).
Then, even if the seller I bought from is from another niche, they are another Fiverr seller, kind of a colleague, in a way - would you tell a random person who emailed you on your company’s email address and asked you about how one of your colleagues is performing?
Thirdly, that purchase was something rather personal, which it sounds like yours might be too, and I had zero wish to talk about my purchase to anyone, but was forced to reply, and felt awkward having to find a polite way to tell them ‘nunya’.
Again, I understand your wish and you don’t have any bad intents or anything, of course, but if you try to take the perspective of the one being asked, you might understand why it shouldn’t be done (asking sellers about their reviews) respectively can’t be done (asking buyers about their reviews).
However, if a seller explicitly states that something may take more than 10 days to manifest, I might see that as a sign for caution because it happens to be the exact time you can leave a review (when the window for reviewing was 30 days, you’d often see “can take longer than 30 days”), then again, if they indeed sell something that takes time to manifest, they might feel the need to protect themselves from people leaving bad reviews before whatever they bought could manifest.
The only honest way for buyers to review such services is to give feedback on the communication from the seller, unless “something happened” within the ten days.
Obviously, it would be unfair to leave a bad review if you bought something that might yet happen, so, typically, you’ll only find good reviews for sellers who sell such things.
You can only search, compare, do a bit of Googling, and hope for the best.
You can also look at all gigs of the specific seller, perhaps they also offer something that’s a bit more “tangible” and or order something like that, or their cheapest offer, to get a better feeling about their behaviour (how do they communicate, are they pushy about reviewing (not allowed), etc.). In case you’d not really be happy with that, you won’t have spent too much.
If you buy something like that, ultimately, no matter how much research you do, you can only trust, or not.
IMO, anyone who wants to buy such services, should do that in the full realization that they might spend their money on nothing, and it better not be the family’s last money, but money they can afford to lose in the worst case, and money that was well spent in the best case.
Hope that helped a bit, or at least added some perspective.