PAYE codes 2016/17

I have just received my P2 "explaining" my tax code for 2016/17, as I'm sure many taxpayers will have. Why are the notes so misleading?
1. Untaxed interest - all interest from banks will be untaxed in 2016/17, but for most people the interest will be covered by the savings allowance of £500 or £1000. So why is bank interest set against the personal allowance?
2. Dividends tax - note says "This is to collect the basic rate of tax due on your dividend income". But the basic rate of tax is 20% and dividend tax for basic rate taxpayers is 7.5%.
In fact the figure of "dividend tax"  in the code multipled by 20% is approximately the amount of dividend tax I will pay at 7.5%. But why muddy the water by saving " basic rate of tax due on dividend income"

I'm sure those notes are going to confuse many taxapyers and accountants. Why can't they be clearer?