I think Z-dad’s point is like this. For those of us who already think OO is kefira, this kol koreh is superflous. OTOH, for those people who like OO, the kol koreh annoys them by what they perceive as another example of religious condescension.
So what was gained by it? Who was on the fence that will now change their mind because of this kol koreh? Probably no one. In which case, nothing was gained, but another wedge was introduced. The OO crowd will have more dislike for such Rabbanim, using this as an example of chareidi condescension. And the ability to mekarev these OO to real Judaism became a lot harder.
Z-dad, am I correct in understanding you?