I am not at all surprised that someone obtained a brick of Macklem-Carney notes. I would be surprised if the prefix was HAE or HAL, but again, not completely surprised. These notes existed in time and space. The odds of a collector getting one are not favourable but still quite possible.
What surprises me more is the seller's decision to post all 10 bundles in one listing. It would be much smarter to list one bundle and see if that sells first. A pair of consecutive HAG notes went for $36 recently, so $18 per note (incl shipping). The brick seller wants $25 USD per note. If he is serious about that price, I must reiterate that showing 10 bundles is a bad idea. It's honest of him to admit he has the whole brick... but honesty and profits don't often see eye-to-eye.
So either the seller is not too bright or there's an alternative purpose to his listing. Strangely, selling 1,000 rare notes at one time makes those notes seem, well, not so rare.
I believe based on the number of Macklem-Carney notes being reported that the Bank of Canada never issued their remaining inventory after the November 2013 launch of the polymer $5 note. The small bump in the number of reported M-C notes shortly after the polymer note release is from bricks that were already distributed. Instead of being returned to the Bank of Canada, some bricks were put into use along with what was already in circulation. So I have to believe that the seller had this brick since at least November 2013. Or he knew of the brick's existence for a while and just ponied up the cost when it became necessary. What we don't know is how many bricks he could have, or, more generally, how many bricks are being hidden by people who don't want anyone to know they have them.
I never meant to infer that bricks of mixed prefixes must contain inserts. It begs the question of what criteria are used to decipher inserts from mixed regular notes, but that is not pertinent to the current discussion. All that matters in the case of the HAG brick having some HAF notes in one bundle is that the HAF notes have not been confirmed as inserts. For ranges of M-C inserts to be known, that requires proof from bricks, and again, that means people need to obtain bricks of M-C notes AND for those people to divulge their secrets. Not surprisingly, there are no M-C $5 insert ranges confirmed. But, for all I or anyone knows, lots of people DID receive M-C bricks and reported finding inserts... but there is still no news from the authoritative source about insert ranges.
So for those of you keeping count, paper money collecting is 98% speculation, 2% fact.