Rust has a long and storied history of bad optimization.
If you don't understand what the words mean, don't say them. You're not helping matters by sputtering pure garbage.
because it runs off Unity
Unity is a very poor engine, but it's not responsible for developer stupidity.
as far as I'm aware Rust has problems with memory leaks
Let's get some more info on this.
Unity uses the Mono framework (JS/C#), which only has automated garbage collection; you can force the GC to collect, but you don't need to (and have no means to) manually clear assigned memory. So long as you're being a bit smart and making sure to call Destroy() when you're done with something in the world, it should be okay (Destroy() marks an object as clear to remove, but the Garbage Collector can and will also search for objects which you didn't explicitly destroy, but aren't being referenced by anything else active in the scene and clear them too).
If the game were to, for example, be constantly spawning objects and keep them referenced and "live" within the world without destroying them, that's an issue. Whether it's an actual "memory leak" or just stuffty programming is down to your own perspective; I personally would want to see what code is responsible for creating these stuff chunks to determine if they actually have a purpose for existing. It could, for example, be particle emitters or audio emitters which aren't being cleaned when they're done, or maybe the game just never unloads parts of the world as more is thrown into memory.
