Of course they can, but that is fraudulent and very different to someone building up their own car. Plus such people may be able to stamp a chassis but they do not know:

Where to stamp.
How to stamp (gang air stamp or individual hand stamp).
Variations in chassis construction not only between plants but through Series.

All of these vary such that most re-stamps are identifiable with enough research.

All a lot of time and effort for such a low return - hardly worth it.