Board Thread:Questions and Answers/@comment-46.42.165.69-20130318195036/@comment-46.42.165.69-20130318201211

Oh! I've found it myself! Maybe somebody will find it useful.

"version - 3.3.x:  Clearing is done bottom layer to top layer. Items dropped can be collected

version 3.4.x+: Clearing is done from top to bottom layer, items cannot be picked up in the first 1/2 second and vanish after a further half second. This change was made to stop the filler being used as a cheap quarry alternative. This can be disabled in the Buildcraft config file by setting the variable 'B:filler.destroy' to false."

http://minecraftbuildcraft.wikia.com/wiki/Filler