WIPMOM, I haven't heard yet from Trinity, but it would appear from upthread that boys who passed Wilson's haven't necessarily been called for interview at Trinity. Yet my DS didn't pass Wilson's, and has got an interview at Dulwich. So I'm not sure it's straightforward.
It's been suggested to me that Dulwich are primarily attracted by a high maths score, and provided the child in question can string a coherent sentence together on paper so they don't have to spend a year struggling to get him to a common level with his cohort, they will take a view on the English - certainly the fact that they've called DS for interview suggests that that's the case. However, your comment that the passage in the interview was complex does not bode well for his chances.
My personal feeling is that English is so linked to maturity that judging boys of 11 on their English standard is a bit of a false premise, but I suppose other schools may believe that a good standard of English at 11 is an indicator of outstanding things to come.
I'm doing this for the first (and only) time, but my instinct would be, comparing Trinity with DC with Alleyn's, that any of those three schools can ensure that the child in question will perform to the top of their ability provided they turn out to be workers and presumably provided that they're happy at the school, which would be more a reason for differentiating, IYSWIM - pick the school he'll like, because any of those three can do the results thing if the child co-operates...