Grid card with decluttering creates gap on conditional (while regular cards dont)

didnt notice before , so not sure if this is new or not, but using a config like:

    - type: grid
      columns: 4
      cards:

        - type: custom:decluttering-card
          template: celebration
          variables:
            - event: birthday_wijke

        - type: custom:decluttering-card
          template: celebration
          variables:
            - event: birthday_marijn

        - type: custom:decluttering-card
          template: celebration
          variables:
            - event: birthday_frederike

etc

and a decluttering template:

  type: conditional
  conditions:
    - entity: binary_sensor.[[event]]
      state: 'on'
  card:
    type: custom:button-card
    template: button_celebration_alert
    entity: binary_sensor.[[event]]

shows a grid alright, but if the first in the set of cards isnt ‘on’, it shows a gap, and likewise for the other positions. I seem to remember the grid fills itself nicely before, but might be mistaken.

However, and this is probably what I remember, if I dont use the decluttering, and write the grid like below all is fine, and no empty grid cell is used:

    - type: grid
      columns: 4
      cards:

#        - type: custom:decluttering-card
#          template: celebration
#          variables:
#            - event: birthday_wijke
#
#        - type: custom:decluttering-card
#          template: celebration
#          variables:
#            - event: birthday_marijn
#
#        - type: custom:decluttering-card
#          template: celebration
#          variables:
#            - event: birthday_frederike
#
etc
        - type: conditional
          conditions:
            - entity: binary_sensor.birthday_wijke
              state: 'on'
          card:
            type: custom:button-card
            template: button_celebration_alert
            entity: binary_sensor.birthday_wijke

        - type: conditional
          conditions:
            - entity: binary_sensor.birthday_marijn
              state: 'on'
          card:
            type: custom:button-card
            template: button_celebration_alert
            entity: binary_sensor.birthday_marijn

        - type: conditional
          conditions:
            - entity: binary_sensor.birthday_frederike
              state: 'on'
          card:
            type: custom:button-card
            template: button_celebration_alert
            entity: binary_sensor.birthday_frederike

why would the decluttering card cause this?
thanks for having a look