I guess the point was there are open source operating systems. However, the claim that there is an open source implementation of every "class" of software, is

I guess the point was there are open source operating systems. However, the claim that there is an open source implementation of every "class" of software, is still too bold. Think about software with proprietary knowledge like teslas autopilot, fpga algorithms for industrial machines, or, to some extend something like SAP.