Since the cowls lock together as a pair, it is not possible leave an odd number unlocked. I was also under the impression this was 2 cowls not 4 this time.
Yes it is 2 cowls locked against each other by 4 locks. Probably locking and latching just one (the forward one) would be enough to fly safely...
The 'enemy action' in this case is poor latch design.
Not too sure about that. If a design is known to be poor, it should normally get special attention by the mechanics. However, it looks more like it gets no attention at all.
Anyway I agree that a latch in a dirty location where you have to knee down to get to it is poor. But it is hard to design it any other way, if you want gravity to close the doors so that the latching can be done by a single person, then this is the only possible design. You may move the handles to the side of the cowling where it can easily be reached and checked and actuate the locks by bowden cable, but that would just create new failure causes. (at the moment these are KISS latches...)
I think the key here is knowledge and attention.