Ignorant question: why buy the Tracking Skill from the Space Wolf Chapter Advances if every Space Marine gets it for free? Typo?

Why give the Tactical Marine the "Advanced Trained" skill of Command if the book lists it as a basic skill? Maybe it's just a Trained skill then? That seems like not a big bonus for being a Tactical Marine...

Are there other oddities like this?

As per the rules, duplications in tables are for future-proofing and compatibility with other products. Ignore more expensive duplications.

Tactical marines gain the Command skill at a trained level, so can roll at their full stat. Essentially it's a free skill.