"piju" should also be accepted
And what a surprise! It is! :o
If it wasn't accepted you have to report by the official reporting tool so that we can see which exact sentence was rejected.
Why is "They only drink water" incorrect?
The plural form is PIJÍ.
Is there a difference between piji and piju? I've been hearing people say chcu instead of chci, but that's a local variation afaik. So what about piji/piju, which one is standard?
Both are standard. Piju is preferred in contemporary spoken language, piji is the older form, more formal, typically used in writing. Note that this is not limited to pít, but occurs (almost) universally in all Class III verbs.
It almost sounds like "pi" only, one can't really hear the "ji" ending
For the male voice? I disabled the listening exercise.