In Sherlock S04E03, when the drone carrying the grenade arrives, Sherlock asks Mycroft about the trigger response time and Mycroft gives a blank look to Sherlock. Then Sherlock re-frames his question and asks him how much time we will have before detonation.
SHERLOCK: What’s the trigger response time?
(Mycroft looks at him blankly.)
SHERLOCK: Once we’re mobile, how long before detonation?
MYCROFT: We have a maximum of three seconds to vacate the blast radius.
Mycroft is as intelligent as Sherlock. He works for the British govt. and himself authorized the purchase of these grenades (patience grenade).
How come he did not understand such a simple question? (consequently Sherlock had to re-frame his question) Why did he gave a blank look to Sherlock?