I still have .NET 3.5 assemblies.
I believe that the setting 'DisableOptimizations' meens that "Optimize code" is not checked. Therefore the setting 'IsJITOptimizerDisabled' is true.
'IsJITOptimizerDisabled' : 'true if the runtime optimizer is disabled; otherwise, false.
http://msdn.microsoft.com/en-us/library/system.diagnostics.debuggableattribute.isjitoptimizerdisabled(v=vs.90).aspx
A release build assembly (System.dll for example) has following debug attributes (use reflector):
[assembly: Debuggable(DebuggableAttribute.DebuggingModes.IgnoreSymbolStoreSequencePoints)]
(This is not the same as actipro assemblies)
Perhaps this is because I am using an old version 9.1.515 ?