Misleading IMHO.
Firstly it is not that new ! we have had a HVDC link to France for decades, underwater rather then underground I know but still very similar.

Secondly to suggest or imply that widespread use of such technology gives protection against an EMP event is very misleading.
The buried HVDC cable itself might well survive an EMP event, but to what purpose ? the power plant feeding energy into this link is unlikely to survive an EMP. The physically large and above ground converting plant would almost certainly be damaged also.

At the receiving end, the HVDC current would be converted to AC at lower voltages and distributed largely via overhead lines and transformers to customers. all this equipment is vulnerable, as is the consumers equipment.

IMO, HVDC is worth pursuing for general energy security reasons in large countries like the USA. It permits of surplus energy in one region being transferred to areas of shortage for example.
Build wind farms where it is windy, solar arrays in the sunniest parts, and hydro electric plants in the optimum places, and transport this energy as needed.

It is misleading though to consider it as a defence against an EMP event.