robust stop and resume of download

You can stop/resume downloads via HTTP too. That's up to the client to implement.

increased download speed with using several http and torrent sources at the same time

Again, this is a commercial CDN. Speed is practically infinite. Without the rather long ramp-up time too.

downloading from peers from within the same network

That sounds like a micro-optimisation for an edge-case.

automatic checksum calculation and redownlaod if needed

Not really necessary for an installer ISO downloaded via HTTPS.

Sorry that I asked. Seems that you feel very offensed by my question.

???

As mentioned, one of the reasons torrents don't make sense here is that the ISOs change quite frequently. I don't have exact numbers here but there's nothing preventing them from changing every single day. The current ISO is only two days old.

Every seeder would have to discard the old ISO and re-download an entirely new ISO every few days or so.

Given that we need the CDN anyways, torrents just simply don't make sense.