What is the significance that "no blade is involved" in threading pipe?
When pipe is cut with a blade it can result in material debris and/or metal filings or oxides inside the pipe.

This is equivalent to dangerous sediments or solids in a gas line which can damage or clog equipment. Pipes cut  with a blade will likely need to be cleaned and/or flushed before use. Imagine PVC filings clogging a sprinkler head.

Using something like a wheel or die should not pollute the pipe interior.