Except for that most of it was not.
A lot of the noise on the screen (and speaker) was affected by radiation from nearby stuff.
I’d think that nowadays, it would be even more so, with way more WiFi and mobile phone signals everywhere. Now sure, different frequencies mean they would affect less, but the cumulative effect would still be more than the CMBR.
Also, I have a flat-screen CRT at home.
This is one condition in which I might like the “If it runs, you get marks” examiners