Dan Robinson
EF5
In recent years, the "official" definition of a tornado (in this context, from the AMS Glossary) has been revised. One of these was to remove the word "violently":
http://glossary.ametsoc.org/wiki/Tornado
Other revisions to the definition are discussed in this paper "A Revised Tornado Definition and Changes in Tornado Taxonomy" by Ernest M. Agee:
https://journals.ametsoc.org/doi/abs/10.1175/WAF-D-14-00058.1
I can't find much about this other than the journal article linked above, but I am assuming the reason was that many weaker tornadoes didn't meet the "violent" criteria in the previous definition.
http://glossary.ametsoc.org/wiki/Tornado
Other revisions to the definition are discussed in this paper "A Revised Tornado Definition and Changes in Tornado Taxonomy" by Ernest M. Agee:
https://journals.ametsoc.org/doi/abs/10.1175/WAF-D-14-00058.1
I can't find much about this other than the journal article linked above, but I am assuming the reason was that many weaker tornadoes didn't meet the "violent" criteria in the previous definition.