Possible Manaflow Band Bug

Not sure if it's already a known bug, but here goes.

I played a game with Manaflow Band on Bard and found that, if you cast his W outside his cast range, he will start walking towards that spot to place his shrine. However, Manaflow gets used when you press W. If you cancel Bard's shrine placement, you lose Manaflow, even if the shrine hasn't been placed. I tried doing the same thing with his Ult, casting it outside his range and then cancelling it. I did not lose Manaflow by simply pressing R, only after it had been cast.

I haven't tested this with other champions, so I don't know if this is intended or not. It just seemed a bit odd.