Sometimes things get stuck in the OS and do not operate as designed. But on my system, I can open a blank Excel book, and save it, then it appears in the jump list. I have the default setting, I believe, to save 10 items in the Jump lists and Excel is set to save the 25 most recent documents.
So, why might yours not be working... could it be related to what folder you are saving them in? Possibly the format you are saving them in? I have tried both .xls and .xlsx. The folder is potentially the same folder as the Word documents I am saving that appear in that jump list, but I have saved documents to a whole range of folders.
Is there a specific number it is showing in the jump list, and does that ever change to accommodate new books saved? It never shows any documents.
Are you saved books tied to another utility? Not sure what you mean, but I am fairly sure the answer is no.
The Excel documents seem to be kept in this key in the registry.
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Excel\File MRU This is full of entries - about 50, but none of them show in the jump list.
The names are also kept in another area with IBits showing before the name.. I do not know if this is the jumplist or something else. Having searched the registry, no key is found with this string in it on my system.
If your Word jumplist is working correctly, I will assume you do not have something set to remove any histories. As you say, I assume if I did it would remove the others, but I am pretty sure I don't.