'in that' is EXPLANATORY and LIMITING. in other words, it explains the sense in which the immediately preceding description is used (explanatory), and it specifically implies no more than that sense (limiting).
example:
my approach differs from yours in that i am more aggressive.
--> explanatory: the difference in aggressiveness is the way in which our approaches differ
--> limiting: there are no other significant differences between our approaches
--
'because', as you say, shows a cause-effect relationship.
example:
my approach differs from yours because i am more aggressive.
--> there could be all sorts of differences between our approaches - some of which may have no direct connection to aggressiveness - but the ultimate source or cause of those differences is the difference in aggressiveness.
example:
my approach differs from yours in that i am more aggressive.
--> explanatory: the difference in aggressiveness is the way in which our approaches differ
--> limiting: there are no other significant differences between our approaches
--
'because', as you say, shows a cause-effect relationship.
example:
my approach differs from yours because i am more aggressive.
--> there could be all sorts of differences between our approaches - some of which may have no direct connection to aggressiveness - but the ultimate source or cause of those differences is the difference in aggressiveness.
