Heya, well it wouldn't be good to lump all deities and temples together and assume they have the same practices. Each deity is different, and they change across time and space. The Tamar narrative seems to be set around Egypt in 960-920 BCE. A very different situation from temples to Aphrodite, Artemis, etc. in the 1st century.

When thinking about deities, we remember that all humans are seen as owned (1 Cor 6:20 etc). Judah was selling his seed to a fertility deity in exchange for abundance. But Judah was 'owned' by YHWH, and so a property violation was taking place. We can imagine the other deity cackling in glee—until seeing himself outmaneuvered by Tamar.

The issue is never the physicality of sex happening outside of ceremonial marriage. The issue in the OT is kids! Jews guarded their genealogies. No intermarrying! Childbearing was policed, for they were to birth the messiah.

The fertility of Gentile Christians is not tracked or policed. The theology is different. What matters to Paul, concerning the pagan temples, seems to be the sacrificial meat. He may see this as the "energy" of another deity entering the body of the Christian—two deities in one temple is a problem. You can only serve one master, as Jesus says.

I don't see any cues in the Bible that ordinary human intercourse results in such "deity violations." It's just touching someone. Esau had very problematic wives who served other gods, but it was the soup & birthright scene that resulted in "porneia" (in Hebrews 12:16).