@Keith_Beddoe You forget what a filter actually does. ADSL, VDSL and GFast signals do not actually pass through the filter. They are on a direct path which avoids it. For a copper phone line those signals are filtered out for the phone only.
They are to prevent someting like this on the phone line.
There are issues with signal leakage into the phone path. With higher frequencies the effectiveness of the filtering will depend on how much the capacitive leakage there is across the low pass filter inductor I would suspect that the SSFP has been designed to minimise this.
There are a lot more additional components, than in a standard microfilter.
Hey all, I called them and asked to verify the appointment on the 25th.
They did verify with Openreach (the order tracking page did not show any progress though).
I am now connected as the engineer came and installed the line on the 25th 😄
They changed the master socket to one for g.fast with both a flat BT plug for the telephone and a RJ11 for the router.
Thanks for your replies!