The devs who made up the names thought they could avoid prosecution by calling an IPO a different name, but I doubt it will work in the long run. As far as I'm concerned IPO, ICO, and pre-sale all mean exactly the same thing.
Yep, they are exactly the same thing. These coins devs are constantly making up new names for "IPO" in an attempt to try and ward off any legal prosecution they may be faced with. And guess what, it's all still illegal. 100% of these developers are illegally selling unregistered securities and it's most common with PoS coins. In fact, I have yet to see a PoW coin that indulged in an IPO.