Looks like it would be a good idea to carry a copy of that letter on the bike if you are wearing an imported helmet that does not have a sticker. Should keep you out of trouble in Queensland, anyway.
Whilst the letter does state that the sticker isn't required, AS1698 paragraph 8 outlines what is required to be attached to the helmet, and believe it or not, that is inside the helmet, not the pretty sticker outside that most people believe is required. The requirement of 1698 to have that information attached circumvents any letter that may be construed as an out to buy a helmet from overseas.

You have NO choice about this sticker/label (inside not outside), so it is irrespective what is said in the letter, this is an AUSTRALIAN Standard and therefore overrides all other legislation in each State and Territory. The Minister is being advised by a bunch of bureaucrats that take a quick look at things, and truth be know the letter was typed by an AO2 that was given a document from some adviser and then out under the Minister's hand for signing on his way to another meeting without knowing what he signed.
The key words are:
"shall" - no allowance for interpretation it must be done;
"permanently" - there always, not just the first few months;
"legibly" - from the latin legibilis that can be read;
I have confirmed this with people that have much more knowledge than I. This sticker, or sewn patch,
MUST be present to indicate that your helmet has passed the standards of one of only 30 (approx) people in Australia that inspect our helmets.
In Queensland:
TO(RUM-RR)Reg s270 Wearing motorbike helmets
(1) The rider of a motorbike that is moving, or is stationary but not parked, must—
(a)
wear an approved motorbike helmet securely fitted and fastened on the rider’s head; and
(b) not ride with a passenger unless the passenger complies with subsection (2).
(3) In this section—
approved motorbike helmet means a helmet that complies with—
(a)
AS 1698–1988; or
(b) another standard the chief executive considers is at least equal to that standard.
Therefore the outside sticker is NOT the main concern to show that the helmet complies with AS1698. This is what a lot of inexperienced officers look for and ticket people on, but the inside information is the real requirement by AS1698.
Whether we like it or not, it is there. I have just had to get rid of a Shoei Multitec that no longer complies because Shoei use stickers inside the chin bar, unlike other manufacturers that sew in the information, and they come off quickly once you upset the corners.