Thanks!
We responded in about 3 weeks after the request came, however, they waited till the 28 days (what they set for response time) expired.
As I learnt it from my MA, the visa applications are randomly assigned to case officers by a computer system, but only for one view. Meaning, when you get a CO first they check it and if they had any additional request your application goes back to an internal pool until the set period (28 days) expires, due to legal reasons for you to have the full time to respond, so you can't say "but I still wanted to upload some more docs" (therefore they won't continue on your case while the 28 is pending, although my MA says there are exceptions in rare cases).
Then the computer will reassign your visa application to a different CO (so you won't have the same CO as it used to be in the old times).