I don't think that's fair criticism of the DfT, the pre covid projected passenger numbers were a lot higher and they didn't require new build stock but stock to be of new build quality (think renatus 321). They did specify standard class seats into London between 0800 and 0859.
I'd expect there to have been plans for 379s to Great Northern but the price from the ROSCO being too high, then killed by covid and then killed by inflation.
Don't forget there was only 21 365 left for peak use on GTR anyway, regardless of covid, however demand could have or if would have changed then yes 30 x 379s, replacement units even better. However in end covid and prices took hold, however if covid didn't take effect plus the pricing, then yes myself I am more than sure,
that original plans would have happened and x30 379s would be on GTR ie x 9 units more than x21 365, so extra capacity. Also it would have given GTR a standard fleet of 700 ,717, 387, 379 for example, for operating purposes, and costs, for example, ie for driver only, ie 379s have cameras on the bodyside, so no need for the station monitors, or when failing, waiting at stations like the 365 did for a dispatcher. St Neots being one of them on a regular basis. Ie delay to train, plus 379 have Aircon, and WiFi, so costs reimbursement that way
So yes sad to say I miss them 365 as well , the invetiable would have happened, and the 379 would have replaced the 365, but would have been a gradually phased process most likely, between May 2022 and December 2022. So 365 in reality have finished a year or so a little bit earlier than they would have. However quite possible the 379s could all well be GTR bound sound.