Empowered Sparks support Gem

Getting some extreme inconsistent behavior with the Empowered sparks support on monk

slotted in to Killing Palm
I'll get the charges
but the "Empowered" attack only seems to happen once, and then only if the next action is a charge spender (falling thunder)

no other quarterstaff attack I have slotted, nor wing blast from talisman seem to get the sparks

Video evidence: https://youtu.be/XWEC2XCXous

I think the issue is more complex than that. To me it appears that some attacks can be empowered by this support and some can't (I only tested with a couple of different skills, but my current assumption is that bow skills and charge generators cannot be empowered. I didn't test crossbows, maces or spears), however attacks that cannot be empowered still consume uses of the skill without updating the empowerment count on the skill supported by empowered sparks.

The steps to replicate this are:

1. generate a power charge using a skill supported by Empowered Sparks (I used profane ritual)
2. observe the empowerment count on the skill (should be 3)
3. attack once with a skill that cannot be empowered by Empowered Sparks such as bow shot, lightning arrow, or (presumably) killing palm
4. observe the empowerment count (should still be 3)
5. attack twice with a skill that can be empowered, notice that sparks fly and the empowerment count goes down
6. attack a third time, notice that sparks are not fired
7. repeat this process changing the number of attacks made in step 3 and notice that it changes the amount of sparks fireable in step 5