One answer about this topic has explained this is because of the varying position of the avatar on the green.
Sometimes it's straight on the money, other times they are skewed to the right area a little, sometimes to the left a little. Sometimes it's skewed a lot.
This position of the avatar, as claimed by the pro players (fmagnets being on of them, I believe) has an affect on how the dots are translating the break.
I can't find the thread but there is a great explanation about why sometimes the dots show a break but yet it's a straight putt.
Sometimes the break shows a straight putt butt it may roll to the left/right.
IFAIK this is unique to WGT (Nicklaus Signature edition had something similar w/ the shifting putter) but this is a challenge that I've yet to wrap my head around.
The moving avatar has an effect on what the dots are telling you.
here are some of those posts about the green dots:
fmagnets: This video might help explain it better.
PhiEaglesFan 'Kiawah grids are exacerbated by the fact that your avatar is typically 20-30 degrees off-center on a lot of putts.'