I didn't check before posting. There is still the working which involves a Chester service terminating at Stockport, crossing all lines at Stockport and blocking Ash Bridge Junction for 6 minutes to get a unit to Hazel Grove though, which ends up running a service only 3 minutes ahead of the following Buxton one. Surely that could have been eliminated now they've secured an additional Hazel Grove path.
No, the 0841 Stockport to Hazel Grove ECS positions the ex-Chester DMU to form the 0910 to Piccadilly. That is in fact 25 minutes ahead of the next service from Buxton and 11 minutes ahead of the next service to Piccadilly. Without it there would be a gap of 48 minutes between successive services from Hazel Grove to Manchester.
The next service in this diagram is the 0948 Piccadilly to Buxton, which obviously has to be operated by a DMU.
The 0759 Piccadilly to Hazel Grove ECS, although timed for a Sprinter, positions an EMU to form the 0821 to Piccadilly. This unit subsequently forms the 0901 Piccadilly to Crewe. Currently the 0821 is formed from the 0722 Piccadilly to Hazel Grove, but that EMU will be used for the new 0751 to Piccadilly.
The 0812 Piccadilly to Stockport ECS just gets an EMU out of Piccadilly after it has finished its morning peak workings. It could not work the 0910 from Hazel Grove, because the DMU would still need to get to Piccadilly as well and so would need an extra morning peak path into Piccadilly.