Blood Tap mechanics

[:1]I am wondering if this is correct behavior, because it is not obvious from the tooltip. As blood spec, I start with my normal set of runes:

F F U U B B

Now, I death strike, which converts a F and U to death runes, and starts their regeneration:

D(regen) F D(regen) U B B

Now, death strike again, which converts the remaining F and U to death runes, and makes them fully depleted as they are paired with runes still cooling down:

D(regen) D(inactive) D(regen) D(inactive) B B

Now, I blood tap. What I would expect to see would be one blood rune converting to a death rune, e.g.

D(regen) D(inactive) D(regen) D(inactive) D B

But what I actually see is a blood rune converting to a death run, *and* one of the other runes becoming available:

D(regen) D(inactive) D D(inactive) D B

This behavior can also be observed with a single DS + BT - when I do this, I end up with one death rune cooling down, and two available. Is there something I am missing about the tooltip that suggests that this death rune should come off cooldown during a blood tap in addition to the blood rune conversion?
Yep, it is supposed to be that way. I have Blood Tap macro'd to Heart Strike so that the first time I Heart Stike, it blows the rune on HS then refreshes it as a Death Rune... which I use on a Death Strike=)

I always keep one Blood Rune up until just before the second recharges so I can make the most of Blade Barrier, and keep a rune available for Strangulate when I'm PvPing as Blood.
It's a bug, but Blood Tap has behaved like that for a long, long time.

http://us.battle.net/wow/en/forum/topic/2416208246?page=3#41
You can also macro in Rune Tap to eat the blood rune right before Blood Tap.

Also gives you the ability to double tap the macro if both blood are down and you want to spawn the death rune and RT with it (if the situation calls for it).