as far as I know for SoC devices these are 2 completely different things.
During production test, the general access to different part of the device is tested, the memory access, the clock frequency respond etc.
But silicon validations tests the whole functionality of the device as well as validation of it's signals for various standards.
For memory, i am not sure anyone does a silicon validation since the production test does mot of the work, except for long term and over the temperature range tests as well as radiation testing.
Cheers,
/Farhad Abdolian