I agree. But it still seems odd they’re taking so long to get the rest in service, if (as was assumed) most delays were to do with software?
I think the original explanation was to order enough 710s for the Watford-Euston DC lines to achieve two things :-
1) That enough 378s were freed up for other duties (iirc the East London Line which cannot take 710s)
2) Increase in frequency on the DC.
No desire to have one type of unit on the DC lines - after all Willesden will be awash with the two classes anyway.
Mind you I have lost track of how many 4-car AC/DC 710s are planned but 18 * seems familiar.
There are 6 * 5-car AC/DC (for North London Lines iirc) ?.
And 30 ? * 4-car AC only for use out of Liverpool Street.
*= They are 4-car for Gospel Oak - Barking, but same for DC lines because that is long enough (currently) and provides a common fleet (I take that to mean a few spare can be sourced from the DC lines where any 5-car unit can cover).
Well that is my (mis-)recollection of the last 2,000 odd posts.