It was adapted from an Optimum Training Volume, which is like the GTV, but it's set up as a 5X5 instead of a 10X10, which is much better in my opinion, but that's another deal all together.
I vary in my opinion on hitting tri's with chest and bi's with back due to already indirectly hitting those two muscle groups when you do chest and back. I prefer (in most cases and for most trainees) to hit bi's with chest and tri's with back, it really depends on the volume that you're working at. The reason why I like to split the tri's from the chest and bi's from the back is this way you get one day of indirect hit to the tri's and bi's and a day of direct hit. I'm a firm believer in the more you train a muscle the more it will grow (as long as you're using smart variables and training parameters).
However, I really think that if you want to achieve the most mass you can, the arms and calves need to have more direct work and this requires a day to themselves. This is, of course, considering that one is doing supinated grip bent over barbell rows, chins, (compound movements) in conjunction with isolation movements.
Again, these are just my personal opinions and you'll get a slightly different view from trainees, personal trainers, strength coaches etc. A lot of times you have to find out what works for you because you can end up doing to much work and cause overtraining which negatively effects mass or even gains at all.
Some other thoughts on this-
I think the arms should be trained like the bigger muscle groups (80-90% range for 4-6 reps). If you were to look at Jack Chevrier, he was able to curl 315 pounds with good form. Skip Lacour can curl 225 pounds for reps with good form and those numbers are impressive. So, in short, if you want your arms to grow, lift just as heavy as you would with any other muscle group.