I believe table starter RB overrides the krill rakeback. So if you are earning table starter RB you are already getting 50% back and don't think any additional krill RB. So theoretically if you played only at 2 - 3 handed tables, you could earn table starter RB but no krill RB.
^this
Tablestarter is basically max-krillback possible. The above is correct, and because we are just getting started many games are short and qualify for tablestarter. If one only took the 7th, 8th, or 9th seat in a game, i.e. only wanting to play full ring, they wouldn't see any tablestarter and that krillback would prop up.
Basically you can almost never pay full rake at SwC, and "full rake" is already very low.
This should really be in the T&Cs for both table starter and krillback on the website.