No, you don't lose "a few seconds" on that. If it even cost you half a second, no one would run it. MAYBE a tenth, in the right car. Doubt even that though.
You're right, just because you don't know anything about drag racing does not make you dumb. However, it makes you unqualified to post about what rear end option is best FOR DRAG RACING. Do you know the forces involved when a transbrake car launches? Do you know what happens to your car when a c-clip axle fails? Just because someone out there is doing it doesn't make it a good idea. Not to mention most g bodies didn't come with one and you have to spend a TON of cash to get a used buildable core, unless you've got mad fab skills and can narrow your own and add your own brackets and ears to it. And if you've got that kind of talent, I can assure you, you'd find a better design to start with. Is it a good axle? yes. Is it a great axle? no. Can you get a better axle for the same investment? YES!
Like Bison said, it depends on the goal. If you have one and it's for a relatively slow car or a street car, use it. If you're building HIGH horsepower and high traction, and you have to find one, it's not worth looking for.