This happens when you quote bad sources.

The big picture: Watts is not a primary source: that would be the actual Greek New Testament.

The details: Matthew 28:19, Jesus refers to himself as τοῦ υἱοῦ (literally “the son”); in Matthew 16:16, Peter says Jesus is “ὁ υἱὸς τοῦ θεοῦ” (the son of God); the demons in Mark 3:11 call to Jesus “you are ὁ υἱὸς τοῦ θεοῦ” (the son of God); in John 1:49, "Nathanael replied, 'Rabbi, σὺ εἶ ὁ υἱὸς τοῦ θεοῦ,” (you are the son of God). I could give more, but it would just get tedious.

Bottom Line: Watts doesn’t know Koine Greek and either 1) he didn’t do his research or, 2) he lied.

More detail: the definitive article (the) changes forms depending on the case and gender of the noun:`ο,`η, το, του, τη, τους, etc. (ho, he, to, tou, te, tous).