Antennas --especially big ones-- have a large radar cross section, i.e., very visible on the radar. So a stealthy ship wants to avoid them. At the same time, long distance communication requires very large wavelengths and therefore large antennas. Temporary antennas are a good solution.
EDIT: this is of course in the article. Note to self: RTFM
But the ability to 'dismantle' the antenna for stealth makes sense, as well as the ability to change the size of it on command.