Originally Posted by
tentseller
There has been trials at YYZ for the general Y line by row number (front Y and rear Y)
In December, at SYD someone was looking at row numbers when people joined the Y queue, and directed the front half of Y to a separate holding queue. This was only allowed to board after (most of) the back half of Y had boarded.
To me it did not make much difference to letting statusless Y board in any order.
While interesting, I don't believe these are the exact same as what the OP is describing. IME, I got an email in advance similar to the OP, and then the boarding pass actually has a boarding number on it. Mine had a big 1 printed on it, and I saw others with different numbers.
I think what you're describing above is the same as what
ultrawin above me is describing at YVR.