Mine has them, and I always wondered what those holes were for. I don't think they put those drill holes in the rim for venting for boiling though. kegs aren't designed and made for being converted into a keggle.
Ohhh I know what happened! Those holes are there to let rainwater out of the rolled rim, and I'll bet the one that asploded was full of water! When it got to boiling, it stressed the metal and kerfloom!
But the most important thing is, the keggle is still useable