Was the 5c Concession Postal Card Rate to Belgium Suspended During the WWI German Occupation? (Updated below!)

According to the rate books, the 5-centime concession postal card rate to Belgium took effect on 1 July 1909 and ended on 1 February 1919.  The postal card rate to other countries, including Germany, during this period was 10 centimes.

But from August 1914 until the Armistice in November 1918, Luxembourg and most of Belgium were German-occupied and German-controlled, even though the lower-echelon civil servants remained in place.  Mail from Luxembourg to Belgium was routinely censored in Trier, Germany. German stamps overprinted ‘Belgien’ were introduced in Belgium on 1 October 1914 and remained in use until the occupation ended.

Did the German occupiers in Luxembourg suspend (or simply ignore) the 5-centime concession postal card rate on Luxembourg to Belgium mail? 

To my knowledge, postal historians have not addressed this question. Consider the 5-centime postal card below, which was posted on 7 December 1917 from Luxembourg-Ville to Liège, Belgium, marked ‘T’ along with a German boxed ‘Porto’ and blue crayon manuscript ‘10’ and  the Trier censor mark:

Then, consider the two 10-centime postal cards below. The first was posted from Dommeldange to Antwerp on 6 June 1917; the second, from Luxembourg-Gare to Brussels on 26 June 1917. Both were censored in Trier and paid a ten-centime rate. Why were 10-centime postal cards used for commercial correspondence when the rate to Belgium was 5-centimes?

   

Check your postal cards and postcards. Do they support my belief that the 5-centime concession postal card rate to Belgium was not honored during the World War One occupation? Was the concession rate reinstated after the war ended?

Update

Dieter Basien and Lars Boetger kindly advise that during the World War I German Occupation, UPU rates were in effect from Luxembourg to Belgium from 1 January 1915 onward.

Here is the revised rate chart for page 76 of Basien & Hoffkamp ratebook, Tarife der Briefpost in Luxemburg 1852-2002, with additions shown in red: