How to retrieve crash logs from TestFlight app in Pre-release testing

I've been trying to get crash reports for my app that is being distributed through iTunes Connect/TestFlight, but am unable to locate them.

I found this thread which states you need to "Include app symbols for your application" whilst submitting to iTunes Connect, which I have done. I then read this thread which states it is only for apps that have been released on the App Store, and does not store crash reports for apps in Pre-release (which mine is).

So, to recap, I have tried:

Making sure the "Include app symbols for your application" is checked,
Installing Xcode 6.3 to view the crash organisation screen,
Waiting ~1 week for crash logs to appear,
Searching in iTunes connect for the app's crash logs.

Is the only way to get crash reports to install a third party reporting tool like Crashlytics, or am I doing something wrong/missing a step?

Solution

Ok, so I have just started getting crash reports for the app in Xcode's crash logs Organizer. This is probably because of two reasons:

I installed Xcode 6.3 via the AppStore, and that fixed any bugs that might have been lying around in the 6.3 beta 4.
I built the app using 6.3 and distributed it using 6.3, which adds some magic sauce. I did the distribution process exactly the same way as before, so seems the logical explanation.

However, ironically, I installed the new Crashlytics from Fabric which I have found to be really, really, really good. It has given me far more in-depth information than Apple's crash logs (your milage may vary). I'll keep using it throughout our apps development, but may then take it out once it goes into production.