4tph down to 2tph Stansteds will be because of covid driver related reductions. The remaining pair call at all of Tottenham Hale, Harlow Town, Bishops Stortford and Stansted Mountfichet (1tph) rather than being spread amongst 4tph.
Also note that the 1H services which are the faster Cambridges calling only at Tottenham, Harlow, Bishops Stortford, Audley End, Whittlesford and Cambridge and thence to Kings Lynn as appropriate are all wihdrawn so the remaining 2Hs will look slower.
In terms of timings as I have pointed out elsewhere other operators slots have to be respected or may be flexed or rejected by NR. Planners are busy right now and keeping train plans simple is both operationally, practically and mentally better for all, including the planners.