It being science doesn't mean it can't be unethical. I'm sure there are loads of biological experiments we could be doing that most would consider unethical.

That said, I don't think I'd call this particular experiment unethical, because it was a free mortgage calculator app and I can't imagine people depending that much on it. Calling it a dick move seems more apt. Then again, who knows...

Psychological studies, when ethically conducted, are opt-in. The subject knows they are a part of a study and has a choice not to be and nothing about their lives change if they do. Here, it is not opt in, nobody knows they are being subjected to experimentation, and it has impact on the subjects that they did not agree to sign themselves up to.