That's reasonable. We should rely on the sentence structure, not on the voice. That adds to my original point: "I am confused, because I am told that I erred when I said 'I am holding it.' Why can't "אותה" also mean a thing that is feminine?" Hoping Duolingo will correct that (if it hasn't already done so), or explain why this sentence structure doesn't indicate that a person or an object (feminine) is what is being held.
What meanings of hold does makhziq mean? Hold as in physically lift something up against the gravity (hold the bag for me a second), or take the grasp of something because of fear of losing it/because it is precious (hold on to your culture)? Stop something for a definite period (hold the sugar production this week)?
You can not aways pin down the meaning of the Hiph'il by expecting "to cause that, what the root means in the Qal". In the Bible הֶחֱזִיק meant to cause to be strong too (לְהַחֲזִיק הַמַּמְלָכָה בְיָדוֹ KingsII 15.19 to strengthen the kingdom in his hand), but the second meaning grasp prevailed already then.