Yes that is true. A lot of ICOs really do use eth. Although there are some that use btc and waves, the majority are eth users. Mostly because the blockchain system of eth is faster. Plus some just go and copy and avoid hard work. which makes it easier for developers to produce another ICO. Which then the greedy people take advantage. Really sucks if you ask me, but there's just no stoping it because there are no regulations prohibiting such.
If you do try to look on those coins as of now the numbers of eth-based tokens is really more than on those Waves or any other coins.