It is common for Bavarias to have optional keels, deep and shallow. Boats of this age were generally poorly documented and there are often errors in what third party information that has survived from the period. It gets perpetuated by brokers and owners "lifting" from earlier sources.
As you probably know, Bavarias like the one you are looking at are only superficially similar to the later more common type designed by J&J. They were also built in a more traditional and expensive manner with more detailed wood interiors for example. They were expensive at the time compared with French boats so relatively few were sold in the UK. The trick that Bavaria performed was keeping the look but stripping out the time consuming labour through mechanisation and simplifying interior fitout with modules built outside the boat. However they kept the same types of hardware and overall both types have proved durable.
Good luck with your purchase.
