Do blocks support transaction control?

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/14/sql-do.html
Description:

Apparently now DO blocks support COMMIT; - which make them more like
procedures than functions.

Tried it with:

create table z (a int4, b int4);
insert into z (a,b) select i, i from generate_Series(1,10) i;
do $$
declare
begin
update z set b = 2;
commit;
perform pg_sleep(120);
end;
$$ language plpgsql;

And while it was running, in another psql sessions, I:

1. could see b= 2
2. could update any of the rows in z.

Is it documented anywhere? DO docs say that do is like function, which it
doesn't seem to be?