i just know about IEO and and after some reaserch i aggre with you.
projects that issue their ICO on exchange or IEO have more credibility than ICO normally, because they already have Exchange as their backs. With Initial Exchange Offerings exchanges will aid developers in making sure that everything is good.
sadly not many ICO issue their project on a reputable exchange because of the high cost.
in short IEO clearly have a low risk compared to normal ICO.
but in the end always DYOR before investing.