The met_data may vary every 6 hours, or at whatever period is specified in the file. However, the nudging is applied at every timestep. This means that every 30 minutes, temperatures and winds are adjusted to be 0.9 times that calculated plus 0.1 times the current met data values. Model output at any time step will be nudged in this way. There is nothing different about these fields at 3:00 vs. 6:00 just because the met fields vary every 6 hours. At every time step, the output would be 90% from the interactive calculation, and 10% from the met data.
The description of the SD-WACCM compset you have copied is confusing, and will be updated in the future. I would not say it is "driven" by met data, but rather "nudged". The meaning of "radiation feedbacks turned off" is also unclear, and apparently has different meanings for SD-CAM and SD-WACCM. In SD-WACCM, the radiative heating from prescribed volcanic aerosols is turned off by default:
strat_aero_feedback = .false.
However, this is likely to change in future releases, as we have recently improved the prescribed volcanic aerosols.
The term "radiation feedbacks turned off" may have originated with SD-CAM, which uses 100% nudging. In that case, they have set the flag:
chem_rad_passive = .true.
meaning that chemistry does not impact radiation. This is not the case for SD-WACCM, however.