It's not entirely clear from that site, but it looks like they just let you batch up a bunch of separate orders in a single spreadsheet, and execute each one of them.
The grandparent post seems to be calling for a service that lets me say, "I'd like to start my own custom-ETF, consisting of A% Facebook, B% AT&T, C% Walmart, D% McDonalds, etc." and then let me invest money that "fund" every so often. I agree this would be a neat service. Currently, if you want a portfolio of specific diversified stocks, you have to either 1. Find a fund that is similar enough to the basket of stocks that you would like or 2. Purchase each stock individually (getting eaten up in commission fees). Both are less than ideal.