Could also just be the realities of production timelines for popular products. For instance, Canon likely knows they can produce x number of units per month. Even if they know what day 1 demand is going to be with absolute certainty, if it’s going to take several months to hit that number should they push back release to hit day 1 demand? Sounds like they may have done that to increase day 1 availability to some extent already. Maybe they just produce enough to get production up to the next bottleneck in the chain (i.e they could have a limit on how many units could be efficiently shipped to some destinations at once for instance) and then announce it, and let production and shipping just continue to meet the demand as it comes. I mean, for argument’s sake, if it would take 6 months of production to meet initial demand, but you can ship 3 months of production effectively at once, why not do 3 months of production, get it out the door, and let production catch up?
The demand may or may not be a surprise to Canon, but there are lots of reasons as to why they may not have met that demand, and lots of reasons to try to meet it. I definitely don’t think Canon would want to delay shipping artificially to say “we were surprised by demand”, but I’m also unconvinced that it would be economically beneficial to delay release to facilitate immediately meeting all demand. If I were betting, I’d say they just didn’t wait for production to catch up to demand before release in order to get the money flowing. But I’m no expert!