Don't think so. I've got the Drivers Eye View DVD of the Victoria line and this isn't mentioned. What he may be thinknig of is the suggestions, raised as far back as 1982, for the Victoria branch to the depot to carry passenger trains, to a new station at Northumberland Park. Studies have showed traffic prospects are gloomy. Not only that, there are problems in building a station. The land next to the NR station is required by NR, whilst the line to the staff platform, on the other side of the depot complex, would need to be resignalled and a new station built, requiring movement of the depot fences.
The idea of a branch to Northumberland Park would be to alleviate crowd problems at Seven Sisters.
However, there is also an NR station at white Hart Lane. He could also be thinking of this.