Uglúk worthy? I never read that into that part of the story. Eomer, to me, fights him on the ground due to some other reason - terrain, horse wounded or could be wounded, etc. Eomer singles out Uglúk because he is the biggest orc in the bunch, surrounded by the almost biggest body guards. This group holds together while the other orcs flee pell-mell. Eomer surely realized that this group would take special consideration, and so decided to do his own mopping up. Plus, as a leader, it's his duty
to take down the leader of the opposition.
And more about the orcs: In RotK, when Sauron falls, it is noted that the orcs, trolls and other evil creatures become suddenly leaderless and so try to escape by whatever means. The men, long in Sauron's evil service, hold together and ask for no quarter. So there's clearly a distinction between men and orcs.
Could the orcs be like other hive organisms - ants? Do they live to serve a leader, and are "steerless" when that leader dies? Could this mean that there are levels of consciousness in orcdom? At the bottom of the pyramid you could have drone-like orcs that simply follow orders and aren't really skilled. Above that you have some middle managers who can whip up the troops a bit but not plan large scale battles. And beyond that, you may have some orcs that lead missions, or are breed for specific purposes, and some of these, having to interact with humans, are the most cognizant.
It's these that we'd be discussing, and they may have noticed some idiosyncrasies regarding the human culture, and some may even have considered some of these traits.