Comments that I have heard.....
Cut a "factory" cord cap off, and you void the warranty.
Cut a "factory" cord cap off, and you void the UL Listing.
Don't know IF the above are facts or fiction.
Local AHJ provided this info:
Pool filter mfg (large and in local area) will provide a "factory" twistlock cap & cord upon request, if the unit came with a straight blade cap. I have copies of the mfg "note", and give it to people who are in a bind.
Perhaps Don (Resqcapt19) has some insight on the "rumors"