I still think you're reading into it too deeply. You can easily interpret the two quotes as followed:
Jehantel: Realizing the tactical potential of song, yet loath to set aside skilled archers for that purpose, armies began raising dedicated regiments of minstrels. But the members of such units were no warriors, <PC>. Fair of voice and nimble of finger, these career minstrels could find a place in the hall of any lord.Jehantel is giving you an historical description of how "battle bards" came about. So here I agree with you. So for the sake of further argument, I will call 'bard' minstrel. There are bards who sing just to sing as minstrels, and there are bards who have adapted their abilities for battle. However, this does not necessarily imply that Thancred is just a simple minstrel, especially since we've seen him fight on many occasions. Are we really going to sit here and call Thancred a simple "tavern bard"? To imply that is stating that he is either:Jehantel: Such songs as those performed by tavern bards serve no purpose beyond the amusement of drunkards.
1) Devoid of any tactical abilities in the Bard profession.
2) Lying about the fact that he is actually a Thief under the guise of being a Bard (or minstrel).
3) A Thief who is proficient in multiple weapons.
4) A mixture of 2 & 3.
I state this fact because again, Yoshi-P very recently came out on record stating that Thancred can make use of multiple weapons. He then states the bit about the job system, implying that he has multiple professions as well. I think we can all agree on him being a true Thief underneath it all, however. So I'ma have to continue in the reasoning that yes, he is a Bard. However, he's also a Thief (or whatever they will call the base class), and a Gladiator as well.
The bit about "warriors" as well as PArcher's comment on "gladiators" falls outside of the scope of the argument. This is in the same vein as addressing a mixed gender group with a masculine term. For example, you might address a group of friends with "Hey Guys" or "You guys" -- there might be women in there, but you don't mean they are men, they simply fall under that term. We call ourselves Warriors of Light, but of course we all have different professions in game. "Gladiators" do combat in an arena, but of course they have different professions. They are blanket words unlike differentiating a minstrel from a battle bard.