I'm using version Mekanism-1.10.2-9.2.0.294 and the gas tank will drain the gauge dropper, but won't drain the jetpack of hydrogen.

You're not supposed to be able to drain jetpacks, scuba tanks or flamethrowers of their respective gases.

Out of curiosity, any particular logic why not? I can't say it's something I'd plan to do much, but it doesn't seem unreasonable to be able to get gas out of a jetpack, since I'd imagine they probably would use some sort of universal coupling, should they actually exist. :)