Hey,
I suggest a minor rewording of:
Current:
"The SET and WHERE clauses in ON CONFLICT DO UPDATE have access to the existing row using the table's name (or an alias), and to [rows] proposed for insertion using the special excluded table."
Becomes:
"The SET and WHERE clauses in ON CONFLICT DO UPDATE have access to the existing row using the table's name (or an alias), and to [the corresponding row] proposed for insertion using the special excluded table."
The plural "rows" just reads oddly since in any single evaluation only one row is going to be present in the excluded table for the "existing row" in the target table.
David J.