Having read damn near everything 40k (including everything by Dan Abnett) I tend to agree.
On the other hand, there's a couple usages in 40k that I feel imply that this stuff is actually high tech. For example, plasteel. Just combining plastic and steel together may seem cheap, but it also evokes an image of plastic as hard as steel. So some usages work.
Others only work when read. For example, "electrolume" or "illuminator" reads fine in a book, but when said in a Dark Heresy table top game? Awkward. There's a stylization in 40k that tries to evoke a Gothic vibe, and it has the unavoidable consequence of making common names for things longer and harder to say.
And on actual swear word replacement, again, it's hit or miss. Sometimes you can explain it as language necessarily mutating across the expanse of a billion worlds. Other times, it's the need to get a rating to sell the book to a certain age range (a hypocrisy on GWS's part considering the nature of ANYTHING going on in the 40k universe) and it's obvious. I guess my stance is, if it's worth changing one letter on it, it's worth spending the time to create your own word that is as evocative.
So it's a mixed bag for me. It's a shame that the Black Library
closed down expunged their forums so long ago, they used to have a resource section for writing fan fiction. There was this page in it:
http://www.sfwa.org/2009/06/turkey-city-lexicon-a-primer-for-sf-workshops/ that's basically worth of a tv tropes entry on sci-fi writing. GWS regularly violates some or all of it in His name.