Yeah, I dont understand this dichotomy. IF is largely intended to lose/maintain lost weight ... im sure it can become a lifestyle afterwards but at that point one should have figured out the pattern that works for them.
I only add extra calories if im adding a lot of extra exercise. Anything beyond the obvious needs a dieticians help, not HN.
For people who find it hard to eat a lot at once it may be detrimental to a gain goal, but it has a lot of anti inflammatory and hormone regulation benefits