I believe it was explained that the chapter-specific stuff was changed in editing - in earlier drafts, only the squad leader could access his chapter abilities, but those affected everyone. Now, it seems the other way around: everyone can access their chapter-specifics, but only a Tactical Marine can let his squad mates benefit from them.
Which is kinda sad as it often makes the Tactical marines the only good choice for leadership unless you absolutely, positively need a certain oath.
I'm kinda split on this reading. In my games, I probably will allow each member to access their own chapter power (despite a strict reading of the last sentance of oath-taking on p. 228), so basically:
Squad mode abilities available = abilities from oath + individual chapter's ability
This makes tac marines nice, but a DA devastator still doesn't feel that his ability is left out. Of course, with the increased difference in what is available, it becomes important that cohesion should be spent with the agreement of the group.
Overall, I don't think it breaks things too much. Often the abilities are expensive, so that large of a cohesion hit for an ability that may only benefit one character will probably mean it is not used (unless explicitly useful). Ultramarines will become nice (what with their defensive ability).
Because remember, as long as the players are being challenged, there really isn't an issue with this. The real trick/balance is getting the cohesion right.
Also, at the question as to if I was stating that anyone can benefit from chapter specific squad powers: no, I was not (note that I mentioned the usefulness of the tac marines ability)