The character history sections should tell me all I need to know about that specific character. The "Playing" space could be used far more constructively for each of those characters. Define what an Ogryn is, tell me about the species, not the one I am supposed to play, let me play. If you want to help out a new to the universe player tell them what a Commissar is, what they do, what purpose they serve, not that this particular character is well liked, I still don't know what a Commissar is based on the character sheet.
How big is an Ogryn? How big is a Ratling? Those things need to be on a character sheet to tell an unfamiliar player what these creatures are. Far Larger and Far Smaller are not good descriptors. I qualify as Far Larger than the average man being 6' 5".
Telling me that my character wanders off at inopportune times or that I need to be overly aggressive due to the loss of a friend makes me think they are trying to force player actions in the demo mission more than add to the character background or let unfamiliar players understand anything. This type of information would be fine if these were NPC's for the GM to use. For players this just stomps on what a player brings to the game.
As for discussing politics and mathematics, the whopping 12 Intelligence should tell any player a lot about their character. Combine the 12 Int with the one and only line that tells me anything about Ogryn as a species, that they are slow and dim witted, should tell a player to not do what you suggested.
These are intended to attract new players into the game. Not just new to the system, but new to RPGs. If you have never played 40k rpg before, you wouldn't necessarily know how the stats scale, and so Intelligence 12 doesn't help that much as a guide ("I guess it means I am a bit thick, as it is lower than everyone else's. But how dumb is Intelligence 12?"). Now, to someone who knows the system (and the 40k background), it is clearly really really dumb,
but that is not necessarily that clear to those that don't. And if they are a person who has never roleplayed before? Intelligence 12 tells them nothing
. They don't have that grounding in RPG mechanics that would allow them to make even the barest of judgements. Ok, they might guess it means thicker than someone with a higher stat (but that isn't always a given in every RPG system), but they have no way to judge how thick or how clever that makes them, or what kind of character would result.
I don't think anyone would force you to play exactly how it is stated there, it is purely a guide that can be ignored by the more experienced.
As far as the previous post: I don't think the problem with almost guarunteed success is with the pre-BC rules. It is with the change of the cap to modifier from +/-30 to +/-60. With the original cap the best you could ever expect to get at any characteristic test was 95% (Roll maximum for stats, so 40. +20 for advancement, getting to 60. If you happened to have a homeworld bonus in the characteristic you could be at 65. Get the best possible positive modifier? That makes it 95%. Ok, skills are slightly different, as you could get a skill's base to 85% (65 max stat +20 in skill, and then really easy difficulty could get you to 115. Modifiers could get you higher, but then positive modifiers were much rarer with skill checks anyway, but that would max at 145… frankly, at that point why is the GM asking you to roll anyway? It is clearly an utterly, utterly trivial task). Of course, raise this by 5 for RT, so I guess you could get a 100% chance in combat (but then 96-100 is a miss anyway, lower if using full or semi auto), and another 5% in Deathwatch. Deathwatch had a particularl problem that it became incredibly trivial to get more and more bonuses, to the extent that getting the maximum +60 was quite easy, especially when facing hordes.