GMAT Sentence Correction (SC) | Re: When the reporter asked about the status of the budget

Hi I got a doubt in this question about usage of past perfect continuous.

At that time in past Those people were doing some ongoing action of fashioning a compromise. So why cannot we use past perfect continuous there.

at that time they had been fashioning the compromise and would deliver the message by tomorrow. .

Waiting for replies concerning my question. +kudos if the reply satisfies