I ended up booking using VS, but a data point for searching for ANA availability via Aeroplan: I found ANA F availability on an award flight that showed on United. It wasn't close in, somewhere between 14 and 30 days (don't remember the exact number as I've since chosen another flight). The flight never appeared in AP's search at any point (nor was any other VS-bookable ANA F flight I found and booked later on)

I called Aeroplan, and after getting disconnected for 3 hours and then waiting another 1.5 for an agent, I was able to confirm that it was bookable for about 110,000 in points and about CAD$100 in fees + phone booking charge (don't quote me on exact amounts, I barely remember at this point). I don't know if they would allow holding and then transferring points live. It was also bookable by VS. It disappeared shortly after I called. I ended up not trying again because frankly it's likely many available flights would be booked by the time you get to an agent. I believe there are some ANA flights where with the right transfer bonuses AP ends up being a better deal than VS in points.