Not so. Generator Control Units 1 & 2 plus Bus Power Control Unit 1, are situated on E1 shelf. Generator Control Units 3 & 4 plus Bus Power Control Unit 2, are on shelf E3 at the opposite end of the rack, quite a long distance apart and I find it difficult to comprehend that all of them were flooded.
OK that makes more sense from a design point of view. But as you say it makes it pretty surprising if water got them all.
Thanks - Michael