Lots of MISRA could is proprietary and receives no upstream patches from customers. Still, it's not unusual to deliver a source blob to your customer instead of a binary blob, often for debugging. (But sometimes only the binary blob has the blessing of the vendor, so you can only use the binary blob in your released product)

I would not be in the least surprised if someone has a compiler/transpiler from a higher level language to some C code which checks all MISRA boxes.