I would put a big question mark regarding a 20/20 VA with a NVD. Maybe using some "creative" measurement method?
The export limitations for any NVD from US for quite some time are based on the FOM parameter (Figure of Merit). FOM=SNR*Resolution of the tube.
The limit for UK/OZ/ etc... is, if I remember, FOM=1600, which would be the equivalent to the old specs of the OMNI IV tubes. The tubes with gated power supplies are not exported outisde US. If you want some, you have to look for a non-US manufacturer.
I don't think anyone is "detuning" the tubes. It's just a question of choosing the ones having parameters below a given limit.
Arrakis