Aside the answers that you will get here, there are several topics that has been covered on the subject matter and I think you should dig it out to know more about what you wish to know about, IEO projects was basically introduced by Binance exchange first after the industry was hit with lots of scammers that were using ICO to scam investors, and most investors started running from investing and seeing the method as not safe, so I think they came up with an initiative to see if they can verify some projects deeply before registering them on their exchange and then promoting them to the public as safe investment.

They do their due diligent to ensure such project is a very solid one. That is why everyone is beginning to see IEO as safe way to invest because of Binance, but I think you still need to do your own due diligence too before investing.