Well, having toured Egypt (but largely on my own as a backpacker, not on a guided tour) some time ago I'd say the advice is not bad, just not really relevant for 99% of tourists. It makes the idea of going into the Sahara very attractive if you like a little bit of adventure. But once on the ground you'll see the actual problems are totally different.
The reality is, you can't drive around the Egyptian desert at will. Aside from the Nile and a few major concentrations of tourist traps travel is strictly controlled. Particularly for any independent foreign travellers. As soon as you hit the more remote parts of the country you'll run into army patrols and roadblocks. Most of the desert is off-limits unless you can get a permit. One reason is that plenty of tourists have attempted to explore the desert on their own in the past and got lost, eventually died because it's a very unforgiving place. Second, much of the country is very isolated and foreigners would make an easy target for any armed gangs or simply a bunch of Bedouins intent on taking your belongings.
Getting a permit takes a while to take care of (has to be done in advance) and costs some $ - the usual fees plus bribe/baksheesh. It's generally a PITA if you're alone so at that point most people just give up and join a guided tour. Which is way easier because they'll take care of all the paperwork but they'll only take you to the popular spots.
Still, there are regions where you can't legally travel at all and places where you're only allowed to drive in a convoy. So it's a matter of waiting a few hours, possibly a day or two until there are enough vehicles to make it worthwile. Then the convoy sets off, escorted by a few trucks or APCs of soldiers. Once you get going, you can't stop until you reach the final destination of the convoy. Once there, it's often back to getting a new permit from the local authorities and catching another convoy.
Almost all tourists in Egypt who actually venture into the desert any further than a couple of miles take an organized tour. Tour guides are often shady guys, their Toyotas may be a little beat up but they know the desert and they know their business. They want to take you for a ride and get you back safely because a), they want to get back alive just as much as you do and b), it's bad for business to have customers die on you. The only real danger on guided desert trips is getting ripped off, which is pretty much guaranteed to happen. You can't prevent it, you can just try to keep it down to a tolerable order of magnitude. But all in all, it might still be a pleasant experience. The locals are much more familiar with the enviroment than you ever will and they know how to drive.