Is there any difference in VEC based redirect and redirect when using form based editor?

There is a scenario where customer has implemented 2 activities using VEC and Form based editor. In Form based activity, original page is displayed first before redirect happens (not an expected behavior). However, in VEC Custom code based activity, redirect works instantly i.e. there is no flicker at all.

I've already checked the basic requirements like 

1. pre hiding snippet

2. Order in which scripts are executed

3. Body hiding attribute.

Everything seems to be in place. I just wanted to understand that is this the expected behavior in case of form based activity when using redirects or am I missing some point.