[@Necroes]I forgot and was reminded that Cadians would have a higher knowledge of chaos marines.
As for other regiments, it's at best a need to know basis.
Usually worse.
Since the imperium focuses more on morale than fighting effectiveness. Since if we can uphold that the guard is a very promising career prospect, we can get many volunteers to serve.
The more people know of the horrors of the galaxy, the less they are likely to volunteer.
Since if people are forced, they are less likely to fight well for the imperium than if they think that serving will be awesome and easy.

Of course there are also worlds where this doesn't apply, like Cadia.
Where war is taught from the moment one can walk, where hating your enemy is a class in school.


And the part with the imperial guard being transported since they are not the same as the navy because of the treaty after the rebellion of Goge Vandire. All true.
They are however primarily transported in troop transports. Since they are the ones designed for mass troop transport.

Since it is usually the best solution to have custom designed troop transports for that purpose.
Star wars being a setting which goes the opposite direction, but i don't recall other ones right now.