I was more talking about their recent reliability issues. Sorry, I should have made that clearer.
I've definitely noticed more 4 cars over the past few weeks/months, and looking up SE's formation updates some days confirms it is not intentional and is due to faults with the trains.
Today, multiple 377s on Gillingham-Victoria are short formed at 4 from 8 today due to train faults, including during the rush hour. This is the case too often.
SE should really be worried about ironing out the issues with the existing 375/377 before they take on anything new, in my opinion. If they're already struggling to maintain the current fleet, adding more to maintain will just place a strain on their resources.
I could see this being an issue on their main line services - unlike the 465/466, the 375/377 will be around for a long while yet, and reliability issues only tend to get worse as trains age.
We can only hope SE find a way to fix them.
All of this surprises me - I knew the 465 (especially the BREL units) had a reputation for being unreliable, but the 375/377 have a reputation for being rather sturdy, so I'm not sure where these issues have come from.