Hello,
I realize it is fairly difficult to prove a negative, but can you provide me with a video of Shikaku using his passive on himself 3 or so times in a fight and ignoring 1-2 other allied units? That should be sufficient to get a bug report and investigation on this started.
Thanks!

OK, I just got word back on this. Apparently this is not a bug, but a case of a poor text description. Shikaku is a unit that will give his passive based on unit placement, similar to how the auto function determines placement of buffs on fresh units. I believe that Shikaku will give this passive to whichever unit is placed last among units that all qualify. If you change your unit order placement, you should see Shikaku giving this passive to different units. Additionally if/when they die, he should shift who is receiving the buff.
Please let me know if this works out for you.