In these chord we have a C# (6th) and a D (dominant 7th) at the same time and, since they're only one half tone apart, we generally play them in different octaves to avoid unwanted dissonances. Also it would be pretty difficult to fret those notes in the same octave. So, in this case, we really mean a 13th.
See also how we can mix different colors, textures by adding and taking out notes from the chord. Try all the different combinations and listen carefully at the resulting chords, for example the different 'suspension' or 'tension' created by a 9th or a 13th, with or without a 7th.
Now let's see some 13th chords in the A and in the D shapes.