No, because you can allocate from different arenas if you need to. Using plain malloc may lead to fragmentation, but there's no law requiring you to use a single lowest common denominator allocator for your entire program.
That doesn't contradict his observation. Changing your program to use custom memory allocators can solve fragmentation issues, but that's a much bigger step than the changes required to avoid too many (or too expensive ) full GCs (i.e. tuning the garbage collector directly, gettting "permanent" data out of the garbage-collected heap, minimizing mutations so there's less to scan...).
The only times I've had difficulty solving a fragmentation problem was because a GC was involved, and rewriting the code in an effort to trick some enormous black box into doing what I wanted was a lot more difficult than just writing code that did what I wanted in the first place. ymmv.
I guess in theory fpgeek is right, and his great-grandparent post is in the vein of what I thought of answering. But I guess in practice tedunangst is more right at the moment.
