Depending on the scenario, garbage collection can be multiple power cycles down the road. But you're saying that for TRIM-aware Operating Systems, the drive effectively "hides" the data until garbage collection actually overwrites it. Since you mentioned it, users of Steve Gibson's Read Speed utility were observing bus saturation from just that... the drive returning data without actually performing the reads. Pretty efficient.With modern OS TRIM this is already practically the case. My buddy Krzys demonstrates:
I like to add that even if those drives did not yet actually erase, reading the LBA addresses associated with the deleted files will almost immediately result in drive returning zeros without even actually reading the drive.