Whilst your points are valid, this specific rollout is taking a ridiculously long time. No doubt new and refurbished stock will always have a plethora of issues before coming into passenger service, and it's also normal they will also have faults for the first few months in passenger service.
However, comparing the rollouts of the 707s under SWR, which were also brand new trains, and more recently the 458/4s, the 701 rollout is far from gradual - it's sluggish. When the first 707 was launched under SWR, it did Waterloo-Windsor (same as 701s on their first day), except those ran back and forth all day, morning till night, compared to the measly 2-3 services in the daytime of the 701s. Even more concerning is that it took 6 months to introduce a new route for the 701s, which still uses the same unit as the morning Windsors. One has to wonder if that route would have even been introduced at all if not for the refurbishment of the 458/5s.
By comparison, within 3 weeks of the 707s debut under SWR, a new set of 707 diagrams were introduced, on an entirely different route, yet we are still left wondering when a 2nd diagram for the 701s will come to light. Similarly, the 458/4s have also had more runtime than the 701s, with three diagrams already in service since late June (and a fourth entering from Monday). Another point worth noting is that even though both 707s and 458/4s initial diagrams were only going to run on weekdays, both were able to run on event days and match days at Twickenham, when extra services are required on weekends. Correct me if I'm wrong but we haven't seen a single 701 run passenger service on weekends yet, even if it's just for a match day?
Even the testing of the 707s and 458/4s appeared far more rigorous and frequent than what we've seen with the 701s. The 707s, which had plenty of fault-free tests like the 701s, but also testing across different corners of the suburban network, whereas 701 testing seems to be confined mostly to the Windsor and Hounslow loops, with barely any testing elsewhere.