"It is rice."
Translation:Het is rijst.
In some cases you can use hij as the example gives. However, when you describe what something is, it only can be translated as het.
Another way to approach it is that it can only be hij if the it can be replaced with the noun. To use your example.
- Hij/De film draait in de bioscoop
However, in this case you cannot replace it with (the) rice.
I'm not sure, there's a lot of content, but cannot remember any examples that use it (or at least not explicitly).
To some extent it's important in the sense that you can encounter it in the language.
On the other hand:
- It is generally used referring back to something that has been said/discussed/asked previously and these are all stand alone sentences
- While you can encounter it in the majority of the sentences it simply translates as het. Considering the limitations of Duolingo and the fact that this is mainly a beginners level I believe it would be very confusing to introduce examples like that.