I’d be surprised if this was true, the normalization I mean. maybe sample rate correction, stereo to mono, but that could be a step too far
Easy to test anyway, radically reduce the level of one of two similar samples and compare the outcome once inside
The volume of the samples can obviously be adjusted by levels once inside too, i’d stick with levels that you may find most commonly used in other samples, so you can work from the same standpoint with old and new content … i’d have thought -3dB would be perfect, -6 would possibly be too much unless you want to adjust other content down … plus I suppose it depends on what level any automatic sampling normalization comes in at, so if the DT normalizes down a hot signal by -12dB, you may want to avoid the level mismatch of imported vs sampled by importing lower than you’d normally go
just a thought, but I guess most samples you find lying around the place are in the -3dB ballpark … I suppose it also depends on the nature of the material, whether it’s likely to be stacked and sustained or isolated and brief