BUG #14350: VIEW with INSTEAD OF INSERT TRIGGER and COPY. Missing feature or working as designed.

The following bug has been logged on the website:

Bug reference: 14350
Logged by: Maksym Boguk
Email address: maxim(dot)boguk(at)gmail(dot)com
PostgreSQL version: 9.5.4
Operating system: Linux
Description:

During developing the database structure migration with maximum
compatibility for an outside application code (a lot of views with instead
of triggers to transparently restructure underlying data), I found that one
critical (for me) feature missing.

I expected that I should be possible to COPY directly into a VIEW with
INSTEAD OF INSERT trigger on it.
But reality bite me again.

Test case:

create table ttt(id serial, name text);
create view ttt_v AS select ''::text AS str;
CREATE FUNCTION tf_ttt() RETURNS trigger AS $tf_ttt$
BEGIN
INSERT INTO ttt (name) VALUES (NEW.str);
RETURN NULL;
END;
$tf_ttt$ LANGUAGE plpgsql;
CREATE TRIGGER t_ttt_v INSTEAD OF INSERT ON ttt_v FOR EACH ROW EXECUTE
PROCEDURE tf_ttt();
COPY ttt_v FROM stdin;
Some string
Another string
\.
^C

ERROR: cannot copy to view "ttt_v"

Unfortunately application use COPY to batch load in lot places.
Is this a bug? Missing feature? Work as designed?

PS: if it had been already discussed - sorry, I tried to search mail list
archive but found nothing relevant.

Maksym