Duet Display: refund request refused

I purchased Duet Display and was disappointed that it did not work in the way that I imagined. The display quality was poor and there was clearly lagging regarding the cursor. I started a refund request but was refused.

A few days earlier, I tried notability and also requested a refund. That request was approved. However, I regretted my refund request and bought notability again after the refund was issued.

Apple official support seems to be very obscure about its App Store refund policy. From the users' experience, did the refund request of notability (although I bought it again) affect the decision of the refund request of Duet Display? Is the decision made by developers or Apple staff? More practically, if I see something interesting in App Store next time, should I do a lot of research on it before buying the App?