PBA: R’ Moshe says it is only about Shir Hashirim as a Limud Z’chus on using any Passuk. The basic reason is that Shir HaShirim is the easiest to confuse for an actual love song. We might mean the Torah when we hear “Kol Dodi Hinei Zeh Ba” but that’s certainly not what it sounds like. I could see the S’vara extending to Eishes Chayil. Then again, if I had to guess, I would think that Eishes Chayil (unlike Shir HaShirim) is meant to be true on a Pashut Pshat level as well. When you give Pashut Pshat in Shir HaShirim, you lose what it actually means. Saying Eishes Chayil about one’s wife (as an actual love song) is something Jews have been doing for hundreds of years, if not longer.
DY: This is awkward. You just quoted a T’shuvah of the TZ”E that I was entirely unaware of. B”N I’m going to go look it up right now.