memory: bug or feature

I'm playing with MemoryContextCheck() and I a little confuse now.
How idea is for:
       context->initBlockSize       context->maxBlockSize
Must be a memory block already between this range? For example 
the AllocSetAlloc() if create a single-chunk-block not check it and create
block less than 8*1024 (an example for CacheMemoryContext).

The AllocSetRealloc() not check it too.
                Karel