Depends on how old the tube is and how long it sat on the shelf. Testing NOS that have sat for decades will almost all certainly fail a gas test.
Even new tubes that have sat around for a couple of years may fail the gas test.
Tubes that fail a gas test often recover after 10-20+ continuous hours on the heater. If it doesn't, it likely never will. Some tubes may test gassy after weeks of inaction if they have pin/envelope micro fractures from repeated insertion cycles or 'porous' glass.
As far as sonics, all bets are off. Tubes vary immensely. A particular tube may sound fine in one circuit and not well in another. Additionally one tube may drag down its siblings in a circuit or channel.
AudioPhools lack of evaluation rigor makes most recommendations specious.