Apple's Preview is showing you the embedded JPED composite/thumbnail in the TIFF.
If your TIFF file was saved with any of the TIFF compression modes, it's not impossible that the true size of the file in ROM does exceed 4 GB, in which case your best hope is to recover the composite layer.
When working with files that get to be over 1 GB, the prudent thing is to save them in PSB format.