Just because it's difficult to handle 100% of use cases doesn't mean you can't easily solved 80% of use cases. The suggestion the parent and grandparent comments are making is simply to add a button which combines the previous year's statements (understanding that not everyone's fiscal year matches the calendar year) with all the documents that are already in a separate section named "tax documents" into a single download. More generally, they're just suggesting things like naming the file for January's statement as e.g. "2016-january-statement.pdf" instead of the same generic name as every other month's statements.
Saying that those suggestions aren't valuable or worthwhile just because 100% of use cases can't be accounted for probably isn't the best way of deciding which features should be implemented (and if it were, then it seems like most of their current features should have never been built since they rarely seem to handle even 80% of use cases).
My brokerage account allows me to search for statements and then check off the ones I want to generate a PDF for, they then get combined into a single PDF. Of the three banks I deal with it was the only one with this feature made catching up on my statements so much easier.
Saying that those suggestions aren't valuable or worthwhile just because 100% of use cases can't be accounted for probably isn't the best way of deciding which features should be implemented (and if it were, then it seems like most of their current features should have never been built since they rarely seem to handle even 80% of use cases).