GetMethods from AuthoringScope is never called

There are two threads on the theme:

"I'm working on MPF package containing the language service. I need to implement MethodTips feature.

I've created the class inherited from the AuthoringScope class from MPF and override following methods:

GetDataTipText, GetDeclarations, GetMethods, Goto.

All of these except GetMethods are called ok but GetMethods is never called. "

I did as described in these threads (call the 4 methods StartName, ...) but it did not work until...

ProvideLanguageService(typeof(PRLangServ),

"PR Language",

// resource ID of localized language name

true,            // Supports IntelliSense

true,  // Supplies custom colors

true,     // Supports commenting out code

false, // Supports background parsing

true

If I put EnableAsyncCompletion to true, GetMethods will never be called, if I put it as false, then it will be called.

Why ??? Can it be considered like a bug?