I don't see that 'porneia' is evaluating people's motives in having sex. Let's remember that Rahab, a religious hero, was a harlot, and Samson is not critiqued for the scene with the prostitute in Judges 16:1. These figures are not identified as committing porneia.

Porneia seems to refer to idolatry, which might be mixed up in sexual references, real or metaphorical. But real sex doesn't seem to be a focus. Judah isn't identified as a pornos for Genesis 38. Rather, Esau is the prototypical offender for a scene without sex in it.