I think Vaniver is objecting to the narrow claim of a cycle longer than 24 hours. Without clicking through on your sources, they seem to say that teens have a shifted cycle, not a longer cycle.
In particular, that shifting school later improves sleep suggests that teens have a shifted cycle. If they had an unmoored cycle of longer than 24 hours, the greater light exposure of an earlier start would probably be better.
I think Vaniver is objecting to the narrow claim of a cycle longer than 24 hours. Without clicking through on your sources, they seem to say that teens have a shifted cycle, not a longer cycle.
In particular, that shifting school later improves sleep suggests that teens have a shifted cycle. If they had an unmoored cycle of longer than 24 hours, the greater light exposure of an earlier start would probably be better.