If "melihat" is translated as present tense: "He sees that you are changing" or "He sees that you have changed." If "melihat" is translated as past tense: "He saw you changing" or "He saw that you changed" or "He saw that you had changed." (In any version, the change must occur before any aspect of it can be observed.)
"Dia melihat bahwa kamu berubah."
Translation:He saw that you change.
More translations should be accepted :
He saw that you changed.
He saw that you have changed.
He saw that you had changed.
He sees that you have changed.
I tried the above, and they were all rejected.
At least this is a lot better than the Vietnamese course - in spoken Vietnamese you can generally omit the tense markers, just like in Indonesian - but that course adheres to a strict one-to-one policy of translating sentences, which can catch you off-guard if you are used to using day-to-day Vietnamese.