People seem to be missing a couple of points here. Series Recording is about following a Series WHENEVER it is broadcast. It's not just about a program starting a few minutes late, but actually moving in the schedule. For example, you want to watch some series that is normally on at, say, 8pm BBC1, Thursday. Unknown to you just yet, in 3 weeks time it will be at least an hour late because they are going to show some program with 22 men running around a plot of muddy grass trying to kit a piece of puffed up leather. (or look what happens to Strictly Come Dancing, never the same time two weeks running).
In a week's time you go on holiday for two weeks, expecting your selection of a repeated time slot with a bit of padding either end will catch your favourite program. WRONG. Series Recording SHOULD make sure you do get it - even if they moved it to BBC2. (or in the case of SCD, Sunday's program is in the same series as Saturday's. One setting catches all of them whenever they are broadcast - well it better - not for me you understand).
The other point is to do with the hummy "knowing" the program is about to start and start recording a couple of minutes early. With Series Recording it has lost all concept of time (well almost) and is waiting for the correct data signal. IF you keep the two tuners BUT only allow 1 channel to be recorded, then maybe the Hummy could have a small internal buffer of the "recording" tuner to re-wind a minute or two when it sees the start. But you still might have a problem if you want to record something from a different channel immediately after the first one finishes. So maybe you need 4 tuners, but you only "see" two of them?
Which make me think. How does SR work if tuner 1 is recording from, say, Mux 1, you are watching something on Mux 3 with tuner 2 and you have a recording set from Mux 5. It can't be looking at the Mux 5 data as it's run out of tuners. Does it switch tuner 2 to Mux 5 based on the time then wait for the data stream?