I've found this pdf with an analog notation 3/2 like yours with 6 beamed white notes. They say
that these notes have the double value (quarter notes, not eighth) and they must be played almost legato:
The example on the far right is notated with white notes. It says “On la note aussi de cette
façon6
". In fact, Couperin notices three of the four movements in Les Goûts-réünis in 3/2 time with white notes. In addition, Hotteterre says that this time signature is for slow pieces with pathetic,
tender music is used, and that the quarter notes are inegal (pointé) to be played here like
otherwise the eighth notes in other time signatures. In fact, the white quarter notes look almost like
Eighth notes off. In our transmission we kept the 3/2 time and the beamed ones
white note values doubled, i.e. eighths become quarters, etc. - The sentence starts with
"Pointé-coulé" called. In this context, “coulé” means “supple”. We interpret this to mean that the quarters should be stroked back and forth, but so smoothly that it
almost like legato 7
http://www.guentersberg.de/vorwort/de/g224.pdf
