Someone I know said they were told by a polyamory person that jealousy is what brings people into polyamorous relationships? Because it's a rush or it provides a constantly "new" and "fresh" feeling to the relationship? I said that wasn't true because polyamory is a relationship (generally) like most others and jealousy in any relationship can make it unhealthy. I just wanted to check because I would like to enter a poly relationship in the future but I don't want to be in that kind of environment.
You are correct in that "purposefully injecting and indulging jealousy" is not typically a healthy relationship dynamic, and it is not at the core of most healthy polyamorous relationships.
Your friend of a friend may have been referring more to the fact that some people get a sexual charge out of what we might call "jealousy." Lots of sexual fetishes, kinks, and fantasies revolve around threat, territorialism, possessing a partner, etc. Perhaps the most recognizable form of this is "cuckolding" or "cuckqueaning," though there are lots of other forms it can take: some people like to include the 'sharing' of a partner as part of a BDSM scenario, some people just include spoken fantasies about other sexual partners as part of their erotic flirting or foreplay.
But this is a sexual thing, not a relationship thing. Jealousy is a powerful energy, and most powerful energies can be eroticized. There is nothing wrong with people seeking other partners as part of their sexual play, as long as everyone is on board and all parties understand and consent to what's going on. But in almost all cases, what works sexually isn't the totality of the relationship, and vice versa.
For most polyamorous people, polyamory is a way of being in a relationship, not a way of having sex. But, there are people out there who do center their polyamory around sex and sexuality. This can create confusion and even stigma, which is frustrating, but language is imprecise and the alternative is gatekeeping and in-group conflict, which I'm generally against unless necessary for people's health and safety. The most important thing is to know what polyamory means to you.
Just because someone out there practices polyamory in a way you would find unhealthy or unpleasant doesn't mean you need to! Someone else's definition of polyamory can not and should not define your own relationships! Your job is to know who you are, and what you mean when you use specific terms and labels. This is important when communicating with people in your life, and less so when it comes to correcting or policing other people. So, yeah, it's aggravating that misinformation is going around through your extended circle, but rest assured that you don't have to agree with or act on other people's beliefs.