The 1837 edition switched the word order after the connective adverb thus, from “thus were they” to “thus they were”. However, Joseph Smith did not mark this change in the printer’s manuscript. Nor is there any evidence elsewhere for Joseph Smith (or anyone else) reversing the word order for this particular phrase. The text definitely prefers the noninverted order “thus they were” (with 17 examples). But there are two other examples of the inverted order “thus were they”:
Interestingly, the second of these examples contrasts with an instance of the noninverted word order in the same verse:
There is nothing inappropriate about the inverted word order “thus were they”. The critical text will restore the original reading in Mosiah 11:6.
Summary: Restore in Mosiah 11:6 the original word order “thus were they”; the inverted word order is clearly possible, although it is less frequent in the text than the noninverted word order “thus they were”.