One more stream could very well cause problems. The usual bitrate of throughput required for a 1080p stream is about 3.5-8 Mb/s per stream, depending on compression. If you have less than that available, your stream will lag significantly.
I know from experience that the largest business package available from an ISP in my own North American city s 250$ a month and only offer 5 Mb/s upload speed, barely enough for a single 1080p stream. I'd hope that being in the New York Metropolitan has significantly better options, as well as being a large hotel they may have their own dedicated service or T1 backbone installed.
Regardless, they need to have enough throughput available to handle all three streams, plus potentially other unauthorized visitor streams/skype calls, plus regular traffic from Apex attendees. It's a significant load to put on a network, and if they're uncertain at all the network can handle it they may ask third parties to avoid streaming.
And asking Apex team of volunteers to put out press releases for every tiny logistical detail is difficult. They should be more transparent, true, but they are working hard to make the event a success and you cannot expect 100% perfect coordination and organization from a group of volunteers that has little professional event expertise, limited funds, do it only once a year and almost none of them get paid. So cut em' a bit of slack.
Lastly, literally no doubles event does not have at least two singles events running concurrently. Brawl and 64 doubles aren't being streamed, Smash 4 doubles we only see the top 16, and Melee doubles the top 32 and a tad of pool play at 9pm on Fri. Yet there are over 500 doubles teams with 1000 entrants. Plus Doubles are hype.