This is compressor surge, full load compressor surge is what kills turbos. As has been said, once the TB has been closed to only load that the compressor will see is due a pressure wave bouncing back and forth through the intake tract (where the flutter noise comes from, it differs from what you will hear below) and as well as inertial. This is due to there being minimal turbine flow.
I think that with MAF based ECU's that a lot of the reason BOV's were fitted was because of emissions. This is highlighted by the early versions for some common engines (RB20, CA18, etc) not being fitted with BOV's but by the 90's when emission became tighter then BOV's began springing up on almost all turbo'd variants.