They oversell a LOT. They require you to have memory ballooning enabled, which allows RAM to be taken from your VPS and used for other purposes, similar to what OpenVZ does. The RAM you see in the OS is the maximum amount of RAM allowed, and they separately configure a minimum amount of RAM (which AFAIK you can’t see anywhere) that’s the amount of RAM that’s actually guaranteed.
They don’t let you install the OS yourself; you have to use their images since they’ve been modified to enable ballooning and allow them to periodically push things out of RAM and into swap. If you try to disable their modifications, they warn you about it and eventually start restarting your VPS at random intervals to clear its RAM usage.
They were actually a decent host in the past. As far as I know, they were the first host to ever offer VPS hosting with pure SSD storage, around 12 years ago.
They went from being a pretty good host to a somewhat bad host that oversells and has fake “sales” that say they’re ending soon but in reality they’re running them indefinitely. Some people have a good experience with them, and I’m sure they’re not lying, but even the worst hosts have some happy customers.
A lot of the positive reviews would be from people that barely use any of the resources. If you have a “32GB RAM” VPS but use <1GB RAM to host a tiny WordPress site, you likely won’t ever notice any issues with it.