Houndawg,
There are several reasons why you didn't have to redo basic.
1) Even the Army recognizes the superiority of Marine Corps boot camp. They figure if you can survive that, then Army basic would be a joke. Although, they don't seem to think you can do their own basic once and it be sufficient. They want to make sure you can still march, shoot and do PT.
2) It's possible, but unlikely, that going into the Guard versus the Regular Army had something to do with it.
3) The Army regs changed just prior to my reenlisting in '96. Previous to that, you had to repeat basic if you'd been out 5 years or more. They changed it to 3 years right before I went back in. If they hadn't changed it, I wouldn't have had to repeat basic, as I'd been out 9 days shy of 5 years. They may have had a different standard at the time you reenlisted if it were even further back.
The whole repeating basic thing was good though. I hadn't forgotten how to march, shoot, use the phonetic alphabet or throw a grenade, but I hadn't done much running or road marching while I was out. Also, since I knew the games that the Drill Sergeants played, it was easier to get away with things the second time. I got out the first time as an E-1, thanks to a Field Grade Article 15 for fighting. When I went back to basic, it gave me a chance to earn my E-2 back, and put me well on the way to my next promotions.
Frank