BKB interaction during disruptors agha ulti. Can someone explain whats going on here?

http://www.dotabuff.com/matches/2169117825

Incident happens 33:55 gametime.

OD imprisoments gyro, disruptor drops agha ultimate under imprisoment, imprisoment expires and gyro is exposed to static storm, immediately activates bkb.

Shouldnt disruptors agha mute items? or does it mute if hero in that area has taken atleast one pulse tick from ult?

According to combat log gyro uses bkb immediately after imprisoment expires leaving no damage/tick from static between these two actions.