Flemish Harpsichord makers often made their instruments so the bottom could be removed by drilling out the wooden dowels which held it in place. This enables internal repairs to be undertaken and aids soundboard repairs. My late father designed his Delin harpsichord so this could be done and there was a little movement between the bentside and the bottom of his instrument so I decided to have a look inside. Plenty of internal photos are on my homepage. 
When replacing the bottom, I put in more dowels round the bentside area. These dowels are glued in place, but there is no glue between the bottom and the case sides so the bottom can be removed again should anyone wish to do so in future.

Authenticity has many advantages. 18th century makers had amassed more knowledge than most 21st century makers have. It pays to copy them even if one doesn't fully understand why they did what they did.