User blog comment:FairyRaven/Fairy Tail Chapter 399: Wings of Despair, Review and Commentary/@comment-25111584-20140908093613/@comment-7418318-20140908095016

Maybe they meant that the Crawford's corpse only needed a matter of seconds to start the charge-up sequence of the Faces and the charging itself then also needed some time.

That'd actually be in keeping with the first Face. There it also took (or would have taken) a certain amount of minutes to explode from the moment Ezel activated it.

And give poor Makarov a break. Apart from being old, he likely has to dig through a lot of rubble to get to the underground room below the destroyed guild.