I think loose is the right word.
There are speakers at some of their conferences that are very Reformed in their doctrine.
I have listened to a few over the years who have made it very clear that they dislike liberal views on things like the creation. In fact they point out how not holding to the 6 24 hour (which Keller doesn't hold to) is a very slippery slope.
Yet try to get to the bottom of why they would be in the same organization as men who are not orthodox and chances are you will not get a response.
I have written to a few of them over the last few years and have not even received one response. Some of these same people I have received responses from before on other matters. I also know people who have tried to find out the reason for this, without any response either.
Tom