some of the MBP will do 3 external monitors with the macbook closed. You can go beyond that with a USB to VGA/DVI adapter but support is limited and usually slow.
If you got Displayport 1.2 capable monitors you should be able to put two in series on each port of the MBP. You can daisy chain displayport 1.2.
You are apparently correct. Seems to be the same as some higher resolution like 4k support. The hardware can do it and it works in Windows but OSX cannot. According to what I read OSX refuses to support multiple displays on one DP, which is really sad. Took some time to read as many people obviously tried it on older hardware that didn't have DP 1.2. Apple probably wants only their own overpriced hardware to have such a feature.