I was wondering a few times about those enormous whitelist and pre-sale registration numbers also for other projects. I don't know whether all those registrations have always been true because as you say often times activity is so much lower than what you would expect from such a horde of interested people.
It just seems pretty normal for me, it happens to some other site that is doing ICO as well
1. Most people dont use bitcointalk
2. Even if they do, some dont even have any account
3. Most people discover an ICO from those ICO listing website not from bitcointalk
4. They are burning themselves if they are lying about the whitelisting and such, there is really no point to lie unless they want to create the hype
5. Some ICO use ICO bumping service to help create activity in their thread
Your fourth point is what it is all about, isn't it? If you tell the public that there are 100,000 whitelist registrations, then that suggests there is endless interest in your project and you decide to get in as quickly as you can. Maybe that doesn't apply to you, but it does apply to many other people. It's simply another tool to mislead people, even though they are to blame if they let themselves be misled.