Yes it was kind of strange and i agree that had Charlotte only had daughters her oldest daughter would have become the heiress. WWI resulted in Marie Adelaide's abdication but WWII solidified Charlotte as the country's monarch in such a way that her daughter would be far preferable as head of state instead of a German nephew.
Thank you for calling the attention for this fact.
It is curious that the Grand Duke would favour his younger daughter instead of a grand-daughter issued from his eldest daughter.
Was that a common proceeding ?
Knowing that M.Adelaide never married nor had children, if Charlotte only have had daughters, and since the 3rd daughter Hilda's wedding was childless, Antonia's and Elisabeth's only sons died w/o succession that means that the current sovereign of Luxembourg would be Pr. Rudiger of Saxony, eldest living male descendant of the youngest of the Luxembourg sisters, Sophie, Pss Ernest-Heinrich of Saxony.
But I am sure the Lux parliament would have made amends to the succession law and allow the eldest daughter of GDss Charlotte to succeed her mother.
in 1907 Guillaume IV had the Merenberg line of his brother Nikolaus excluded in favour of his own daughters. Marie Adelaide would succeed him and after that her male descendants, the same rule applied to his 5 younger daughters making them in essence males for the line of succession.
On the website of the Grand Ducal Court you can find a short description of the act under droits de succession.
Luxembourg has an interesting history of succession laws. Grand Duke Guillaume IV made all of his daughters equal to male dynasts so had Marie-Adelaide married and had a daughter each of her sisters would have been before that daughter in lin of succession.
Where do you find that breach in succession making Charlotte Marie-Adelaide's suceessor in case if the latter had married and only have had daughters ?