The value calculated in https://github.com/elastic/beats/blob/master/metricbeat/module/system/diskio/diskstat_linux_test.go line 88 does not align with the documentation:
https://www.elastic.co/guide/en/beats/metricbeat/current/exported-fields-system.html
system.diskio.iostat.request.avg_size
The average size (in sectors) of the requests that were issued to the device.
type: float
Diskio metricset calculates bytes and does not simply pull the sectors value from iostat. The documentation needs to be updated to say bytes instead of sectors.
I accidentally created a github issue before posting here: https://github.com/elastic/beats/issues/14204