My guess is that the GC will eagerly wipe+free "secret" memory first and completely on the pass as opposed to deferring to the next GC cycle as is the normal use that may otherwise happen on longer GC cycles to keep overall performance characteristics happy.

This is just my own speculation, I don't know the internals of Go beyond a few articles I've read over the years. Somewhat more familiar with C#, JS and Rust, and even then I'll sometimes confuse certain features between them.