Boltar wrote:

I'm not aware of any plans to change the changeover point.

I believe the latest plan is to move the changeover to City
Thameslink. (originally it was Blackfriars)..

Whats the point?

The point is that if the panto gets stuck up or down, the train can't
proceed and will need to escape into the City Thameslink sidings rather than
get in the way of the other trains. Merely sending the train back might not
be an option when the other line is already carrying 24tph which have to fit
punctually between other services in South London. Farringdon will no longer
be suitable as a changeover point because there will be no escape route when
the platform extension forces closure of the Moorgate branch. I am not sure
why Blackfriars was ever considered as the changeover point, especially
since catenary would increase the visual intrusion of the bridge over the
Thames.