I believe you should go with your gut. Business is business and if you’re willing to work to their specifications, meet their deadlines, and do reworks without being published or paid, I would say the organization lacks integrity and is likely seeking to use their interns as free help to get the publication off of the ground.
It’s one thing to decide you want to work for free, but if there is an agreement of compensation, then the Editor should make good on his/her promise.
If you don’t feel good about it, cut your losses, take the lesson and move on. Writing is a hard business and I can’t tell you how many times I have been stiffed by shitty people in need of my vision and/or writing services. There are all kinds of people in the business of exploiting writers these days. There are also some people who simply never satisfied with the work of others. It could be the differences in cultures, a lack of respect for diversity, a little narcissism. ..who knows? What you DO know is there is a dead cat on the line, and it’s stinkin! Never underestimate your gut. It’s a warning. Waiting too long may not be wise. Think about it, do the pros and cons list, then make a decision. Don’t invest in someone elses dreams while failing to invest in your own.