For a simple explanation...
You can't completely simulate the difference that way, but it's good enough for practice and certainly better than nothing. It really depends on what type of shooting you're doing...but if you were really into precision shooting, I guess you wouldn't be asking.
The best way to think about it is this:
The target may look smaller at distance, but it's not actually smaller.
And to make it translate completely, you'd have to be able to hold your particular MOA out to an infinite distance...and there are many factors which make that not likely.