Repair leaky White Rodgers gas valve in Attwood water heater

Having lapped in 100's of valve faces and seats I understand what you have done.

Only problem is although you have a shiny clean seat area it is not flat, properly angled or concentric because of your 'technique'.
The rubber plunger if flexible enough will mate with the valve seat area but may fail/leak due to age, loss of elasticity and imperfect seat area.

Keep close eye (nose) on it when in use........your quick check was too short to prove 'serviceability'.

Much safer to replace with new style gas valve.