That bridge design is also an attempt to solve a problen -- the tendencey of string pull to cause bridge lift. By separating the bridge pin area from the bridge itself, you still get the downward pressure on the bridge that charges the top, but the strings don't pull the bridge forward or up. (The strings are ramped more steeply than on conventional bridges, so there's actually more downward pressure on the saddle).
Not sure what kind of hardwood they use for the bridge pin area or how they attach it, but I've never seen one that's come uncoupled from the top or been damaged from use, etc. It seems to work.
I got interested in Alvarezes after finding a cedar-topped model at a yard sale somewhere in Missouri while I was on tour some years ago, one of the best sounding guitars I've come across.
A couple years ago I bought an Alvarez Yairi DYM75 cedar-topped guitar, which has this bridge design. Also a great sounding guitar.