Just to consider the opposite viewpoint, I sometimes wonder if it's not better that they do churn in that case.
Assuming the sales team is doing their job properly, there are other prospects who may not need that feature, and not ramming the feature in under time constraints will lead to a much better product.
Eventually, their feature will be built, and it will have taken the time that it needed, so they'll probably churn back anyway, because the product from the vendor they did get to ram their feature in is probably not very good.