I don't think that buying ICOs through exchanges is a good idea. Not only are you putting your trust on the devs of the coin, but you're also trusting the exhcange on top to secure your coins.
Yes I agee with you. Exchanges can do shady stuff with the ICO results because it has zero to none transparancy. I am sure alot of small exchanges are doing this, but because there is no prove of it we can not do anything about it. Also fake volume can be done so others will invest too in the ICO.