Updating the extension manager (extension list) needs 30MiB per Update..
Since you have fixed the "update" for the extension manager (extension list) (Slack entry in typo3-cms on Tuesday 29th August 2017, 12:31AM) it looks like it downloads the full list (30 MiB table volume) of extensions on every update. My scheduler task is set to 600 seconds (10 minutes).
Could it be that the extensions.md5 file on typo3.org/fileadmin/ter/... is changed every few minutes?
The update process must be another like the last few years cause our binary logs are blowing up to ~ 4GiB per day (tx_extensionmanager_domain_model_extension) for this table only (Scheduler planner: update extension list every 600 seconds). Would mean: Every 10 minutes (6 per hour, 144 per day x 30 MiB = 4320 MiB)