"Bug" implies a mistake/oversight where the additional functionality was known to noone, and then discovered. This functionality was deliberately created, thus it's a "backdoor".
Based on what seemingly passes for "accepted practice" in the mobile world (download QPST for tons of fun!), the only sane way to have a trustable mobile device is with a separate cell-modem and a well-defined interface.
I mean, maybe I'm confused, but this sounds like they closed one method (among others) that could potentially be used to create a backdoor by, I guess, a carrier or OEM.
There's no evidence that anyone's phone was open to remote exploit at any time.
Based on what seemingly passes for "accepted practice" in the mobile world (download QPST for tons of fun!), the only sane way to have a trustable mobile device is with a separate cell-modem and a well-defined interface.