Seats were new for the 442s when Southern did the refurb.
Same style as what FGW (at the time) had in their HSTs.
I think the reason for the 442s is that they can have them immediately (albeit after whatever needs doing to them).
In theory they could have them right now, but last time these were out of use for a while they weren't exactly reliable at first - one even set itself on fire at Brighton, IIRC. And some of them have been in cold store, so goodness knows what condition they're in now. Plus, those Southern interiors... :-\
Before you all leap on my back, as a passenger I really don't understand the 'emotional attachment' that many people seem to have to the 442.
Most of those who travelled on these trains when they were new, and during their time with SWT tend to remember them as extremely comfortable trains. (Obviously with any train there are people who don't like them!) Based on the Mk3 carriage, fitted out with compartments in 1st, comfortable seating throughout, good ambient lighting, excellent ride quality... there was a lot to like. Travelling on these was a generally pleasant experience - especially with the snug next to the buffet for a comfortable pint on the way home! And for those who cared about such things, the EE546s make a fantastic sound at top speed. So unlike a lot of other trains before and since, they had a lot of character. They were the flagship of Network SouthEast in their day.
Given that plenty of Mk3 based carriages are still in daily use, it's not a stretch to suggest these could be kept in use for a while longer. A full re-fit and re-traction would bring them up to modern standards, and as the Mk3 bodyshells are (presumably) believed to be in good condition, it makes sense.
There have been rumours that the odd one might end up on a Weymouth service, or at least a Poole... I can only hope!