Inserting skillgem in wand with inserted gems in sockets make skillgem disappear

I found out today then one should not put a skillgem, with support gems socketed, to a spellslinger dueling wand as this makes the skillgem disappear. One support gem will be inserted into the wand's sockets, the rest will go to inventory. The skillgem will disappear.

Bye bye lvl 19 +20 quality skillgem.