scan.nextcloud.com doesn’t seem to have a high priority. It can be very useful (e.g. like the certificate check at ssllabs) but only if it is working… we shouldn’t have feature that we are not able to maintain.
Documentation is a good point. There was even a talk about it on the last conference:
Even if new features are announced and some time available, there is nothing or very little about them in the documentation (e.g. end-to-end encryption).