The process you mention is for a "hot plasma" formed by electric sparks. Presumably this companies technology uses "cold plasma" aka non-thermal plasma which is significantly more efficient and more selective toward HNO3. Heres a good review paper: https://link.springer.com/article/10.1007/s42768-021-00074-z

Here's another interesting one: https://pubs.acs.org/doi/10.1021/acssuschemeng.9b04997

There is still some NOx production, but likely low enough enough concentrations to be filtered.