Sync in app web not possible?

@vgrem  referenced me (didn't help) to Sync button for Document Library created with custom list definition in order to resolve the issue I am having.
Here is an issue:

I need to have a library in SharePoint-hosted app that can be synced via OneDrive Sync Tool in SpOnline.
as of 4/29/2014, I can't make it happen:

The sharepoint-hosted app has a library. Once deployed (SPOnline), I see the instance. 

The sync button is disabled on the doc panel...

I have checked the  Sync button for Document Library created with custom list definition and did as prescribed, but the issue remains. 

Here what I did as the article said:

1. Checked the feature id that delivers the list and list instance:

FeatureId="7ea48d05-ba84-4553-b5ab-0d02118c86f4"

 2. Modified element.xml:

in the list template:

• changed the type to 101;
• added FeatureId="7ea48d05-ba84-4553-b5ab-0d02118c86f4";
• changed DocumentTemplate to "10000".

in the list instance template:

• changed the type to 101;
• added FeatureId="7ea48d05-ba84-4553-b5ab-0d02118c86f4".

 After that, re-deployed to SharePoint Online:
The sync button is still disabled

If somebody knows solution, please help me out!
Thanks

P.S.
The same wsp from App deployed as a sandboxed solution on the same site collection does allow me to sync docs from the lib

P.S.S.

And here is almost official response: NO, APP WEB LIB WON'T SYNC