I'm sorry I didnt run away I just went to bed lol I posted at 4am mine time like today except its 5am. Maybe I am misunderstanding but from my perspective I don't think gaara can get away fast enough. Idk what his flying speed is or if databook stats are just based on them running but it says his speed is average. We also dont know how fast the nanos spread but if Diedara was confident enough in the jutsu that its his last jutsu before he pretty much has to kill himself. so I imagine it must be pretty fast if he feels he can rely on it to that extent. But I'm just speculating.
You've seen Gaara cover an entire village with a Sky Sand Defensive Wall in the time it took for the Bomb to go from falling to exploding.
You've seen Gaara gather enough sand to stop an exploding Jokey Boy from decimating an entire division within a second.
You've seen Gaara Travel on his sand in the war arc and keep up with Oonoki & Naruto KM while on the move.
You've also seen how quickly Gaara's sand can move to catch it's prey/target.
You've seen Gaara's sand block A's Guillotine Drop and Sasuke's Amaterasu.
Gaara's sand is very fast. He get get away in time.