benchmark: shorten pipe-to by reducing number of chunks

(this only now start taking a long time due to #49552)

without this, it takes 2.5 hours with this it should take around 15 minutes:

each iteration (single combination) takes 9 seconds (saw here).

there are 16 possible combinations. so 9 seconds * 16 combination * 30 default runs * 2 versions = 2 hours and 24 minutes...