Absolutely, you are the company paying for all the work of the FOSS app, having to ensure it meets FCC regulations for banking. It’s a huge mess. Costs millions to do. Pull requests can’t just be taken they must be studied by several teams and a lot of the time it’d be easier and better if that code came internally so you’d be able to directly communicate with the author. That said FINOS exists, www.finos.org They are more about adopting the usage of open source libraries rather than writing their own though.
Overall you’d get no to little benefit and lose a competitive edge while causing more technical headaches following standards to open source your code.