It changes it to a general statement. The sentence you wrote would mean "THE apples [specific apples as opposed to apples in general] are big."
I agree. “The apples are big” should be accepted on the grounds that “apples are big” sounds like you are talking about apples in general, which aren't big compared to say watermelons; “The apples are big” makes sense because it implies that certain specific apples are particularly big. (I myself bought some particularly big apples at a grocery store a few weeks ago.)
But that's exactly why the sentence includes "होते": right or wrong, the speaker IS generalizing about all apples. If it was THE apples, the sentence would be, "सेब बड़े हैं।"
It's also true होते used as habitual form होते means now it exist and will continue to exist in the future
If apples are (generally) big then I wonder how you'll describe watermelons!
What this means is something along the lines of "Apples can be big" or "apples are usually big."
If you were to just say "apples are big" in Hindi it would mean "the apples are big" because we don't have a word for "the" (we do have a word for "a" though).
Why not, "सेब बड़े हैं", I thought the conditional tense "होते " is only used when what is described is the inherent quality of an object, like "the grass is green". Here, big-ness is not necessarily a characteristic of an apple.
No, but for the purpose of the example we are treating it as if apples are generally big. The statement doesn't have to be true to life to teach the point of grammar.
True. But when such a fruit as jackfruit, or watermelon exist the acceptability of this sentence points more to it being accepted in the colloquial language, rather than to "the point of grammar."