`.done` only applies to the first line of a TODO block? Why?

Hey,

I usually answer my DONE todos in a line below in the same block (Shift+Enter). Unfortunately, this second line does not have the .done CSS class assigned. At least it is not stroked through, when done. I also tried overwriting the .done property but it is still only applied to the first line. Is this a bug or a feature? Seems not intuitive to me…

Kind regards,
Max