RETURN NULL in the sample of insert trigger on partitioned table

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.6/static/ddl-partitioning.html
Description:

Why in provided samples of "insert" triggers on partitioned table at the end
of the triggers you provide "return NULL" not "return NEW"?

This causes, among other things, problems with the GET DIAGNOSTICS clause
var = ROW_COUNT clause.