I posted the video below on YouTube that shows this behavior in 12w50a. The mining progress is only reset if the block you pick up is put into a slot on the hotbar.
I did use the search; this is not the same bug as MC-2920. That bug has to do with how the line is shown when using the pole to strike. This bug is about how the line appears when NOT striking. Please re-open this bug report.
I posted the video below on YouTube that shows this behavior in 12w50a. The mining progress is only reset if the block you pick up is put into a slot on the hotbar.
http://youtu.be/tuN0ppa1A6M