Configure entity tags (Etags) in YSlow

[ADDISON74]

Chrome browser + latest YSlow
Varnish (80) + Apache (8080) + PHP + MySQL - basic configuration
Magento 1.9.1 + Turpentine extension (this makes Varnish work for Magento)

I am checking my page content with YSlow. It is Magento home page version 1.9.1 using Varnish/Turpentine combination. I was very happy seeing "Add Expires headers" and "Compress components with gzip" with an A value. This means Varnish/Turpentine are doing a great job together. There is no need to load Apache modules Expires and Deflate.

I have an issue related to "Configure entity tags (ETags)": I got a grade F, "There are 19 components with misconfigured ETags". Let's take one of these 19 components and check the header: http://192.168.159.123/media/wysiwyg/slide-1.jpg

HTTP/1.1 304 Not Modified
Last-Modified: Thu, 27 Feb 2014 06:19:42 GMT
ETag: "e4afd-321ae-4f35d4e89bb80"
Content-Type: image/jpeg
Cache-Control: max-age=604800
Content-Encoding: gzip
Accept-Ranges: bytes
Date: Mon, 08 Dec 2014 10:57:22 GMT
Age: 1294
Connection: keep-alive

As you can see, ETag is set up by Varnish. Now let's visit only this component alone in browser and check it with YSlow. This is the header, same like the one above, but YSlow now shows a nice 100 value grade A:

HTTP/1.1 304 Not Modified
Last-Modified: Thu, 27 Feb 2014 06:19:42 GMT
ETag: "e4afd-321ae-4f35d4e89bb80"
Content-Type: image/jpeg
Cache-Control: max-age=604800
Content-Encoding: gzip
Accept-Ranges: bytes
Date: Mon, 08 Dec 2014 10:58:39 GMT
Age: 1371
Connection: keep-alive

I don't understand what is going on really. Because in whole page content, all things together, these 19 components appears having an ETag issue, but taking them individuals they have no problem! Same header in both places. I guess this is a bug related to YSlow behavior.