There are good reasons not to use Fortuna-as-written nowadays, so I don't fault Linux that. But it would be nice if someone familiar with the design published something like the Fortuna whitepaper, or Microsoft's Windows 10 RNG whitepaper[1].
(Why not use Fortuna as-written? The main reason is that it is not designed to scale. It's a reasonable design for the single core machines of the era when it was written, but it does not worry about contention at all. You could also swap out AES for Chacha as PRF, because: Chacha is faster to seed, faster to generate on machines without AES-NI, and doesn't have some of the theoretical problems -- discussed in the Fortuna chapter -- that AES has with its relatively small 128-bit blocks.)