I applied to Harvard as an international student back in October but, like most people, was unfortunately deferred. however, after 3 days I got an email from a senior admissions officer that wanted to talk to me through Skype and during our Skype conversation she was joined by an admissions director at Harvard. they advised me to apply to Andover academy, a prestigious boarding school, because I was too young for college ( 15 back then ) and told me that if i decide to do so they will send my Harvard application instead of me applying directly. However, I was unfortunately wait-listed there and I was later also wait-listed at Harvard. I also survived the wait-list rejections harvard sent out and made it to the second round of waitlists. after being waitlisted on ivy day, I got an email from the same AO recommending me to consider reapplying to Harvard for fall of 2021. as i was not admitted to any college this cycle because i applied to very few, i am planning on reapplying but i am not sure how good/bad my chances are at harvard and whether i should REA to harvard or ED to a less competitive school and play it safe. Harvard is my dream school and I would love to go there but at the same time i really don’t wanna waste the early round boost. any insights on this are welcomed 
They are clearly interested in you. Its not typical for Harvard admissions to interview someone. And then to turn around and encourage you to apply again next year. I’ve never heard of something like this happening.
It sounds like you have a unique profile that they are very interested in. So I wouldn’t waste this opportunity, just apply again.