You know it is not something that I ever discussed with anyone - as far as their own perspective - maybe it was something that they did know and I didn't. My comment arises out of my own experience. It was until much later in life (not sure if I was an active JW or not at the time) when I realized that what other Christians called "Grace" JWs (we) were callking UK. I know that few if any JWs use the term Grace, when really, since JWs do accept usage of alternative translations, they ought to use the two terms interchangeably more often than they do. yet I have known few that ever use the term Grace. (one would think, that just in an attempt to relate to others, they would use the term Grace or say both of them together so that a non-JW would understand what they were talking about.)
But it is interesting to note that actually even the term undeserved kindness is used sparingly or is rarely found in oral conversation or expression. Generally, the term seems to be used most frequently in written form and usually in the limited context of discussing Jehovah God's "provision" of his Son, Jesus, as a Ransom.
If this is so, as I think it may be, it is probably reflective of the larger JW theological view which emphasize one's own part to be worthy of Grace (i.e. "works"). This is obviously in contrast to the "do-nothing" Christians who emphasize Grace and believe that works are irrelevant to Salvation.