I doubt that Bobbleheads would add a perk or a rank of a perk you potentially don't meet the requirements for. That would really mess up the balance of the level and SPECIAL requirements, I think. My guess is that they either do nothing at all, or they offer unique perks like magazines.
And I hated how the bobbleheads (and implants, for that matter) made it a bad decision to set one of your SPECIAL stats to 10; although now that there's no level cap, and you can pick a perk as soon as you meet the SPECIAL requirements, it's not really a big deal any more.