Depreciation warnings

I'm working with Rails 3.0.0.beta4 and found a spot where the input
controls in the form disappeared. The code was using the old-style
block notation (<% rather than <%=) with fields_for in a deeply nested
form. So, a fields_for was nested within another fields_for. There was
no depreciation warning in the server output.

I suspect this might be a "won't fix" but I could log it in Lighthouse
anyway. Recommendations?

Also, what's the official policy (if there is one) on what deprecated
means? In my experience, sometimes depreciated rails code still works
but you get a warning. Other times, I've seen it where the code
doesn't work anymore and still you get a warning, which seems more
like "unsupported" at that point.