Yes, that's true, I started with a ready made Twitter account of 3,400 followers.
What I was really showing is that a Twitter account is like a traffic tap for an autoblog and can switch on an instant flow of traffic to an autoblog that has been set up like this.
I could delete the blog that I created a few days ago and then rebuild it and then plug the Twitter account into that one. If all my traffic was coming from Google and I removed my site then rebuilt it on a new domain I'd lose all of my rankings and traffic.
As you mentioned, if you get 100 people per day to follow you back then yes, it will take 30 days to get 3,000 followers but in reality it will take longer as you have to wait to see how many of the first 100 follow you back, then unfollow the ones who don't follow back, then follow another 100 and repat the previous steps.
It could take a couple of months to reach 3,000 but you may not need 3,000 and you never should be relying on just one autoblog for your income.
The autoblogs are super simple to set up which means all you need to do is work on your Twitter accounts.
Here's the secret: Set up 10 autoblogs and then work on building up 10 Twitter accounts (each one linked to one of the autoblogs). If you're building up 10 Twitter accounts then you can reach your 3,000 followers 10 times quicker than you would if you were just working on one Twitter account.
You don't have to have 3,000 followers all on one account. I have 105,000 followers over 24 related autoblogs. Can you imagine how long that would have taken if I'd of worked on one account at a time?