64-bit executables don't have built-in memory limitations, y'see.
They sure do. To be fair, you are hard pressed to actually hit these limits, but they do exist!
Most current CPUs that implement the AMD64 architecture (which is what I assume you are talking about) only provide a 48bit address space, which gives you access to 256 terabyte of memory. Usually the address space is divided in high and low 128 terabyte areas with a hole in the middle. As it turns out, the internal word width doesn't need to reflect on the external address bus width.
I'll grant you that you will have a hard time to hit that limit, at least as long as you are staying within the virtual address space only. The physical address space is much much more limited (go figure why), and it's easy to hit that limit on 32 and 64bit.
Not saying that 64bit isn't good, in fact, Gamestudio
should be 64bit, but saying that 64bit doesn't have memory limitations is an illusion that is going to bite you in the ass if you stick to it.