Absolutely untrue.
"A memory leak is where the game have a error in the coding and loads something infinitely or in a looped amount of times to where the size will infinitely increase." This isn't the definition of a "memory leak", and the examples given are not accurate. Memory leaks can happen for various reasons : dereferencing a NULL pointer (an initialized pointer that doesn't point to anything), losing the virtual address, never freeing allocated memory(which is what the examples you gave are, they load infinitely, therefore the process never reaches the point where it gets them freed).
Now, changing the priority is NOT supposed to work. Telling the operating system "please, change this process' time slice" does not work. Setting a higher priority MAY only increase performance, as the process (game) will have more reserved CPU time for it's threads, however, in some instances it could decrease the overall performance, as both the process and thread scheduling algorithms will jump from processes/threads less frequently, because of the game reserving much more CPU time, but this shouldn't be noticeable if your PC's are good enough.
Now, let's explain "real-time". Real-time scheduling algorithms are ones, that give the virtual execution units exact, fixed CPU time, no more, no less and system interrupts cannot preempt the threads in order to run other elements (other threads) from the ready queue. It's Microsoft, so I assume they implemented soft real-time scheduling, where a little more or less milliseconds is tolerant. If anything, this will only cause the game to crash more often (if it goes beyond or below it's given fixed time slice) and almost 100% certainly should slow it's performance.
Experiencing less crashes after changing the priority is just a coincidence, telling the CPU to give more or less time for execution to something will not fix memory issues. This isn't magic, this isn't how it works.