Why is 1 the default value of r.RHICmdBufferWriteLocks?

With r.RHICmdBufferWriteLocks set to 1 there’s an aditional copy through a CPU buffer when Locking/Unlocking vertex and index buffers using Vulkan and, for some reason, D3D11.

The description of the variable reads “Only relevant with an RHI thread. Debugging option to diagnose problems with buffered locks.”, which indicates it’s a debug feature and should be off by default.

Why is 1 the default value?