I am not an expert of Wikidata but I work a lot in integration of databases with several middlewares or tools.
I think that the best way is to ask a solution to store and to download data in a format compatible with datasheets like CSV.
Excel is considered also a tool to do some basic analysis, but it can be connected easily to a data source (if well structured).
Excel itself is not a good approach to store data, so it's not a good solution to keep the data in excel format in a database.
Doesn't make sense to store a 2D tables in a database in my opinion because the data have no sense and they are not helpful to anyone.
They can be stored like a text file, but I would not imagine the series of errors that can be generated importing these data again.