Oz Nidviru is the shailos u’teshuvos Sefer by HaGaon HaRav Binyomin Zilber zt’l. Kovetz Teshuvos, being from Rav Elyashiv zt’l, is widely available.
You’re extrapolating from a sefer that is extrapolating from the CC, and you’re assuming this discussed scenario with non-frum Jews fits within the parameters of the listed criteria. But that’s your assumption not the sefers saying. I, on there other hand, am citing a direct and specific psak that it is permissible to speak l”h about the non-frum.