Before addressing this particular flaw (that is not unique to the LSB), I want to stress that the Legacy Standard Bible is an excellent translation of the Bible and I highly recommend it for reading and studying. With that said, however, it still retains several flaws that modern translations have yet to address and correct.
"SEXUAL IMMORALITY":
Like many modern translations of the Bible, the LSB continues to retain the false interpretation of the Greek word porneia as "immorality," "sexual immorality," or "marital unfaithfulness." This word is correctly interpreted as "fornication." An examination of every passage where this word is used will show that if you let the Bible interpret itself—in context, in none of these passages does this word mean anything more than illicit sexual acts committed by unmarried persons (single, betrothed [engaged], or widowed). It does not include incest, homosexuality, bestiality, prostitution, harlotry, etc., nor does it include adultery.
There is a difference between fornication (porneia) and adultery (moicheia). Unfortunately, many false teachers lie and claim Jesus provided an "exception clause" for divorce with regard to adultery (marital infidelity). If this were so, why then does Jesus use the word porneia in this "exception clause" while every other reference to adultery He uses the word moicheia? Because of this glaring problem, these false teachers lie further and claim that the word porneia includes adultery. If this were so, why are there so many passages that use both words side-by-side (Matt. 15:19; Mark 7:21; Gal. 5:19; 1 Cor. 6:9; Heb. 13:4)? If adultery were included in the word porneia, it would be redundant to add the word moicheia. If the word porneia includes other sexual acts, such as homosexuality, why are both words mentioned alongside each other (1 Cor. 6:9)? Again, if homosexuality were included in the word porneia, it would be redundant to add the word arsenokoites. When this word is understood correctly, it keeps us accountable for our actions and restricts our behaviour. So let's get our terms accurate:
Adultery = Illicit sexual acts committed by married persons. (Post-marital)
Fornication = Illicit sexual acts committed by unmarried persons. (Pre-marital)
It is imperative to know that the Bible does not combine all sexually immoral behaviours, such as homosexuality, bestiality, pedophilia, prostitution, harlotry, etc., into the word "fornication." This is a false claim by many Bible teachers (found also in many dictionaries and lexicons). Look up the 7 occurrences of porneuo, the 10 occurrences of pornos, and the 25 occurrences of porneia in the Bible and let the Bible define the meaning of these words. Therefore:
The Bible uses the terms adultery and fornication to address both physical and spiritual sin. When speaking of physical sin, adultery is illicit sexual acts committed by married persons (currently married or previously married [divorced]), while fornication is illicit sexual acts committed by unmarried persons (single, betrothed [engaged], or widowed). Adultery is only applicable to married persons, while fornication is only applicable to unmarried or single persons.