YEs, it is true for most ICOs. Some are now implementing lockdown period for Bounty/Airdrops to avoid Dumping.. Why complain if it is a free coin/token right? It will be released once it reached the target Market Cap or Period.
The lockdown of tokens to avoid dumping might seem like a good idea on the surface but from my experience this has not prevented dumping of Airdropped tokens . The best it does is postpone the dumping!
Yeah i believe some ICO implemented this one and also the airdrop tokens is distributed later. Some project also has a good plan to lessen the dumping by distributing the tokens by batch and it helps a lot.