What is important in multi-crew operations is keeping the other pilot in the loop.
Therefore it is necessary to announce what you are about to do. That might well have been prompted by “DRAG REQUIRED” alert message. Your SOPs will specify the wording.
Why would you want to deploy the SB when the TLs were not in idle?
You use SB during the descent ( LVL CHG) to increase the ROD.
You might use it in level flight to increase the rate of speed reduction.
When additional calls are called for by a company over and above “Boeing standard”, it probably due to a previous event and management is now trying to mitigate future threats.