Why is my Contribution Detail Report (native CiviCRM Core report) not accurate?
Ok figured it out: the report is fine if I remove the column ‘Credit Card Type’. Then I see $100 in the report!

So if you select column ‘Credit Card Type’ a non-credit card contribution like this chq are aggregated over the number of financial transactions associated with the contribution, b/c the field ‘Credit Card Type’ lives in the Financial Tables. 

So this is definitively a different bug from the one referenced here as well; this bug is related to (unnecessary) financial transactions.