Your post #62 is quite clearly implying that EMR trains were being delayed unnecessarily, see here: "So they purposefully timetable slow running Thameslink on the fasts that make inter city trains late sometimes... Odd". Even though
@Bald Rick explained what is really happening, your next post #66 persists claiming that here is some deliberate action to make TL trains delay EMR services. Anyone who has travelled a few times on the TL fasts know that the waits for EMR trains to get into TL territory do cause delays to TL services, - which in turn can cause further delays to GN line TL trains waiting in the Canal Tunnel. A frequent problem is late TL trains being held at Harpenden waiting for access to the fasts to West Hampstead. The impact then is the TL train stopping at St Albans and sometimes West Hampstead causing the following EMR train to hit yellow lights down to the Belsize Tunnel, - no doubt you would see that as TL timetabled just to slow the EMR services down. If on the other hand the signaller decides to route the TL trains on the slows, stopping at St Albans, it either gets tangled up with a Sutton loop service at Radlett before it can cross over to the fasts, also messing up the sequence entering the core, or the metro service gets messed up a lot south of the river.
There is a reason why the Thameslink services are all running under 9XXX codes, - because the service is very tightly timed with short dwell trains that are required to clear the (much higher than EMR) volume of passengers travelling. Giving them a higher priority than ordinary express code 1XXX services allows the more critical service to take precedence.