From what I've been told, they pour the only real two-piece cores in the industry. I've heard also they are really hit or miss and you have to be precise or the reactions on some of the balls can be over/under.
So far as I can tell right now, after I and a friend drilled 2 of them, this is not true.
Their cores and shells are not very different, in general terms, with regard to RG and Differential and pin placement than several others. I took an educated guess with the Exodus solid, based on BJI's review of it, and I hit the nail on the head. I couldn't have gotten better use from it UNLESS Tony watched me bowl on my lanes and told me how to drill it. A friend did the same with the Pin Hacker, a pearl, and also got excellent results. I gave him what I knew about the ball and a copy of BJI's review of the ball, and he took it to his pro shop with that information to drill.
If someone told you drilling their balls are hit and miss, my guess is they made a mistake and chose the wrong ball and/or wrong drilling for their delivery and the oil pattern they face. I'd suggest checking out an expert like Tony (who seems more than glad to answer any question on the use of these balls) and/or checking out professional reviews like BJI or a pro shop you trust.
FYI Roto-Grip, Storm and Visionary still make some 2 piece balls: core and shell with no filler.