Form Based Activities not rendering with "Apply Propositions"

A form based activity was created which was available in the network response call but not on my website  when I was using apply propositions . My apply propositions was implemented in the following manner : -
 

To make that available on the website , I have to explicitly add the following custom code

var prop = event.propositions.find(
  p => p.scope === "appinstall-popup-mbox"
);
document.querySelector(
  "#abc-membership > section > div > div"
).innerHTML =
  prop.items[0].data. Content;

 

Is there any optimal way to do it or the reason why a seperate custom code is required.