bug or feature? fixtur and . +next not working with different amount of dotted fixtures

SW 3.4

when i have a selection of fixtures with a different amount of dotted fixture numbers the fixture+next selects only the amount of dotted fixtures equal to the amount of the first fixture in the selection.
1 = 1.1, 1.2, 1.3, 1.4
2= 1.1, 1,2, 1.3, 1.4, 1.5, 1.6

1+2 enter,
Fixtur+next = 1.1, 1.2, 1.3, 1.4
Fixture+next= 2.1, 2.2, 2.3, 2.4
2.5 and 2.6 are not selected

.+next results in 'loosing' the fixture withe the smallest amount of dotted fixtures:

1+2 enter
.+next=1.1, 2.2
.+next=1.2, 2.2
.+next=1.3, 2.3
.+next=1.4, 2.4
.+next=2.5
.+next=2.6
.+next=2.1 (1.1 is 'lost')
.+next=2.2 (1.2 is 'lost')
.+next=2.3 (1.3 is 'lost')
.+next=2.4 (1.4 is 'lost')
.+next=2.5
.+next=2.6

in both ways (. or fixture) ALL results in the correct selection.

Grtz
Pepijn