Hey there. Nope, official interviews are not part of the process at Columbia. I've just heard back unofficially from my future PI at Columbia but no official letter yet. Good luck with your apps!
Wow, Contig-- really strong application. I applied to Columbia E3B as well. Apparently they took in a really large cohort of students last year and thus are very few spots this year. Eek. Faculty meetings are happening later next week to discuss applications, I've heard. Good luck!