The trick is doing so in a way which requires basically zero hardware. DIY ergo keyboards are built around a controller like the Pro Micro - which can't do this

The trick is doing so in a way which requires basically zero hardware. DIY ergo keyboards are built around a controller like the Pro Micro - which can't do this out-of-the-box. Having to add a bunch of components to implement such a feature isn't really worth it when switching to USB-C also solves the problem, at basically zero cost and effort. It's not spec-compliant of course, but who cares with DIY?