No. The article makes the mistake in thinking the the Radio part of the GSM bandwidth is the same as the Network bandwidth. It's not.
To continue the FedEx example, an SMS is like a post-it was was stuck onto your package. Trouble is the post-it might be going to a entirely different recipient to the parcel. So it's only piggy-backing until it reaches the sorting office.
Some networks work by store and forward of SMS much like email, others attempt direct delivery first. The point being that, if the recipient's phone is turned off, unlike a voice line you can't just give a busy signal (or charge extra for voice mail).
Where the article falls down is it's ignoring that the network understructure needs to handle and route SMS not just carry then from the handset to the mast.