Why is no thumbnail in purchase book as subscription one?

I suggest in web reader for purchased comic must have thumbnail one as we have in chapters from subscription magazine.

I need to fast forward by click next endlessly or use skip button one to another chapter when chapter from magazine can be select which page I want to look without skip or start from first page of book or chapter, it's not convenient for me and maybe others.

Thank you.

It was stated some time ago that eventually book and subscription chapters will be both readable with the premium reader, but it's not certain when exactly this will happen.