THAT for THAN

THAT for THAN

The passage below is from The Lucifer Effect By Philip Zimbardo.

https://books.google.co.kr/books?id=Jz8IMDPNYIIC&pg=PP10&lpg=PP10&dq=powerful+than+we+think,+or+that+we+acknowledge,+in+shaping+our+behavior+in+many+context&source=bl&ots=VKXUKHOGt-&sig=JFE_pkJzAalMueCaFA_yLT7qOsw&hl=en&sa=X&ved=0CCMQ6AEwAWoVChMI2bbhvanIyAIVQ5WUCh3EeAtw#v=onepage&q&f=false

Had I written this book shortly after the end of the Stanford Prison Experiment, I would have been content to detail the ways in which situational forces are more powerful than we think, or that we acknowledge, in shaping our behavior in many contexts.

I'd like to ask a question regarding the underlined 'that'.
It seems to me that 'that' is actually playing the role of 'than'.
(Am I right?)

Then, how didn't the author use 'than' in the first place?
Is there any logic for this usage of 'that' or, though I don't think there is any possibility of it, just a typo?

Hope for your replies.

Regards.