Is there a reason why "rain falls" is not an acceptable translation of יורד גשם?
it's just not accurate because יורד גשם means it's raining and not the direct translation of the words. i guess. יורד גשם can only mean the context that it's raining and not anything else. hope that helped
"rain is falling" and "It is raining" mean basically the same thing, the former is just higher register. It should probably accept both.
there is no verb for "raining" so you can't say "it is raining" literally.
you can only say "rain is falling" - יורד גשם.
if you said זה גשם it would mean "it is rain."
ll המטיר means "to make rain fall", so it requires a subject (like a cloud or God).