My Form 3 hasn’t arrived yet, but the very general rule in stereolithography printing is to avoid presenting the release surface with one huge flat region of your model. Problem being that it greatly increases the lifting force needed (ie, put a huge glass plate at the bottom of a swimming pool and try to lift it off — even if grabbing by the edge or corner)
If you were to compare the actual slices of each orientation, the angled one ought to have profiles with smaller surface areas; presumably easier to peel off the rigid release surface (Form 2 vat)
Admittedly, I didn’t follow this rule much with my EnvisionTEC and B9 printers. Jewelry-focused build envelope of my EnvisionTEC never stressed the stretched FEP vat, and my B9’s sliding vat would horizontally pull the PDMS layer away to sidestep that hydraulic suction. This is what got me interested in the Form 3; the idea that I’m no longer dealing with flat surface (model) against flat surface (vat).
The Form 3’s flexible bottom vat might make this ‘rule’ obsolete entirely or partially, but it’s clear that PreForm is going to follow the established guideline for now.