Additional SQL Server features and topics not covered by specific categories
On Standard Edition you can only have Basic Availability Groups. If they can be clusterless, I don't know. But they cannot be read-scale, since you can only have one secondary which cannot be readonly.
As for the documentation, on the page you linked to, I see:
That is, Enterprise-only.
The footnote 4 says:
Standard Edition supports basic availability groups. A basic availability group supports two replicas, with one database. For more information about basic availability groups, see Basic Availability Groups.
But this does not imply that clusterless AGs are available in Standard. You could argue that the footnote is superfluous and serves no purpose.