That has nothing to do with that - you seemed to recode major parts of the output buffering mechanism, whereas adding chunk support shouldn't be more than changing 20-30 lines in the code.
I don't agree that only chunked buffering makes sense - in the vast majority of cases, full output buffering would be fine. With very large output, chunked buffering is probably better.
agreeing, both should be available, I ever wondered why we are unable to define the size of an output buffer (these started by ob_start(xyz) and the main (standard) buffer)
It would be nice to be able to configure both of them with settings like "unlimited" (which would allow the user to flush() it's output as far as he thinks it should be put out) and some "specific size" like 1024bytes or 1000000bytes, whatever
some sort of ob_start('test',2048) would be handy
andré