I could replicate the same error on OSX El Capitan with Mulab from http://www.mutools.com/ too, so I guess the same fix should be applied for Mulab as well. Maybe it's necessary for even more hosts which do not support the "hasCockosViewAsConfig" extension.
That said I'm wondering why the cocoa wrapper window actually should be kept open by default and should only be closed for Renoise and Cubase. The host has no access to this window, but only to the original carbon window, so it's very likely also not messing around with it. Seems more likely that OSX' behavior of released (wrapper) windows changed over the past, now no longer automatically closing them when "releasing them to death"?
I noticed that the 32-bit VSTs will have the same White Widow problem in the latest Reaper. I'm working with an older Juce (3.0.5), so I don't know if something has changed in the meantime. Anyway, adding getHostType().isReaper()) to the if() statement fixes the issue for me.
I'm also wondering what other hosts will have this issue. It looks like Live doesn't need to be added to the conditional list, but Cubase, Reaper and Renoise need to be added (for Juce 3.0.5, at least).
I also wondering why people are running 32-bit VSTs on Yosemite and El Capitan in the first place, versus 64-bit VSTs, or the 32 or 64-bit Audio Units. But that is a different discussion.