formations with 3 defenders dont use all DCs?

[wasabimousse]

I imagined 352 (3412, 343 etc) in TO use 3 central defenders for the back line.
But I just saw what tactics is using the guy from the same association. Only 1 DC and DL DR.

Mine (2nd image) has only DCs.


Anything I should know? My three players might be too close together anyways.
But I couldnt move them any further, as it turns them into DLs/DRs.

Cheers