While I didn't watch the second video, the first one appears that the tube remained in cutoff and he did not apply bias current or RF drive. If a mistake were made here I would expect the Grid and Fault indicators to turn red. It's not uncommon for an amplifier to remove screen voltage as a means of placing the tube into cutoff although I could not see the schematic clear enough to confirm that. It also appears that this amp is well protected against faults such as operation without plate voltage.