Christopher must not have thought it was inconsequential or he wouldn't have changed it.
Norman Spinrad wrote that it was neutronium. Therefore, it's neutronium. Accept it, technobabble some way around it without changing it or simply ignore it. Don't rewrite the past.
In "The Cage", the Enterprise crew were armed with lasers. By the time they started the series proper, they changed the name to phaser because lasers don't do the cool things or work the way TPTB wanted them to.
These are minor retcons. It's not like it makes any more difference to the overall tapestry of Trek than Kirk's middle initial being R or T.