Finding files by file extension

I'm trying to search for files in the web UI based on file extension. If I look at https://dataverse.harvard.edu/dataverse/harvard?q=(fileType%3AJupyter+fileType%3Anotebook) I see about 2547 results as of today of ipynb files. If I look at https://dataverse.harvard.edu/dataverse/harvard?q=ipynb&types=files&sort=score&order=desc&page=1 I only see about 272 files and most are not ipynb files (just mentions of ipynb in the metadata). If I look at https://dataverse.harvard.edu/dataverse/harvard/?q=%28fileType%3AWord+fileType%3Axlsx%29 it shows files for MS Word.

I would expect that the web UI search would also include file extensions and not simply an interpretation of the file extension (which in the case of xlsx Dataverse seems to believe it is not a spreadsheet but Word). Plus searching by file types in the advanced search assumes you know the Dataverse name of the file types supported (why not put this in a dropdown list or have a reference to the file types that Dataverse supports) and allow searching by a simple file extension.

Start by reproducing the two file-extension searches in the web UI and compare their results with the advanced file-type search. No files or tests are named; done means extension searches find matching files and the supported file types are discoverable without requiring users to know Dataverse's internal names.