Correct, raising the banners 5 star pull % will increase your odds of getting the focus unit per pull (compared to getting a 3 or 4 star instead). It won't change the chance of getting that specific 5 star whatsoever in regards to the other 5 stars on/off rate though because once the 5 star hit is successful it will select your 5 star based on the current pool and the % increase focus units have among that specific pool.

Some people here just have a really weird relationship with math. Hence why there was public outrage over Cupid "Stealing" on rate chances during Monster Hunter banner when he was actually just eating your chances at getting random off rate 5 stars.