I completed the entire Echoes of the Future mission on normal difficulty in a total of 9 mins yet did not recieve the acievment for activating the tendrils within 4 mins.
Along with the bugs for the “Contract Saviors” an “Band of Brothers” Achievments
I got the achievement. Maybe you have to get 2 tendrils within 4 minutes of STARTING the mission?
You should see it pop up as soon as Zeratul finishes talking at the 2nd tendril
Hmm maybe ill give it a go cheers
During my first attempt i thought it meant activate 2 tendrils within 4 minutes of each other, similar to a few campaign Mastery achievements, but it did not work. So during my second attempt I finished the whole mission in 4:02 and it was rewarded to me, so i think it’s pretty safe to say you need to activate 2 tendrils within 4 minutes front the start. Ironically there is an achievement for Nova’s campaign that actually says within X minutes from the start, guess it’s just some wording error they didn’t pick up.
GL hunting 
You need to finish it 4 mins into your mission (timer on your left above the mini map). It’s a very easy mission actually. All the best.
Thanks for flagging this up, I will include this into the list:
I complete the whole mission in 3:45 and did not get the achievement.
Im doing theese archievments just now lol. Parkour with Zeratul, get the first two tendrils in the first 4min of the mission.