See this page about the meaning of porneia:
biblehub.com/greek/4202.htm
Seems more like “fornication” or “sexual immorality” than unlawfulness to me.
This is interesting. Your own link has something you didn’t mention. Here’s what the link has (emphasis mine):
4202 porneía (the root of the English terms “pornography, pornographic”; cf.
4205 /pórnos) which is derived from
pernaō, “to sell off”) – properly, a
selling off (surrendering) of sexual purity;
promiscuity of any (every) type.
[See also the contrasting term, http://biblehub.com/greek/3430.htm”]3430 /moixeía (“
marital unfaithfulness”).]
In other words, if Jesus had meant infidelity He would have used moixeia.
Here are a couple of quotes from CA articles on their site:The word “adultery” is not what Jesus said, although many Bible translations use this word. If Jesus intended to say adultery, he would have used the word
moicheia, meaning “adultery,” but instead he used the word
porneia, meaning illicit or invalid.
One clarification: Jesus appears to be making an exception when he implies that divorce and remarriage could be permissible when the cause of the divorce is “unchastity” (Matt. 19:9). However, the word used for “unchastity” is the Greek word
porneia, which can be accurately translated as “unlawful lust,” such as “incest” (Spiros Zodhiates,
The Hebrew-Greek Key Study Bible, AMG Publishers, 1984). In such cases, the original marriage would not have been valid and the bond never effected, so no adultery would occur with a second marriage. Here we see the scriptural roots for annulment, which does not end a marriage but discerns that a valid marriage, for specific reasons, never took place.
It seems to me that if God said married people become one, and nobody is to pull them apart, it would follow that divorce would be wrong, and that He would be contradicting Himself if he allowed man to then pull it apart.