Shot attempts are meaningless, what is meaningful is that the actual shots taken by Mtl. were of the extremely dangerous variety, which I'd think implies that the lesser team is actually more talented or had a far more pronounced killer instinct.
Alright let's do it like this then. Montreal took a grand total of 7 shots on net in the 3rd period, which by your description is total domination. Here's a description of all 7 shots:
1) 18:36, Jake Evans chips the puck in at the Leafs blue line and it goes on net. Kallgren covers it. This was very charitably considered a shot by the Toronto scorekeeper.
2) 14:49, Anderson hunts down a puck lobbed into the Leafs zone and gets there first. He doesn't have any time or space to do anything other than backhand it on Kallgren. Anderson has 1 backhanded goal in 59 games this season and it shows. Easy save for Kallgren.
3) 13:37, Gallagher speeds past the Leafs at the blue line and gets a good scoring chance on Kallgren. Would I say this was an extremely danger shot vs. just a dangerous shot... eh, but I'll give you this one.
4) 4:38, Romanov, who has 3 goals in 69 games this season, puts a puck on net from the Leafs blue line. It wasn't a particularly hard shot and it wasn't tipped and there was nobody directly in front of Kallgren. Also want to make note of the times here, in a period where the Canadiens apparently had "pretty much total control" they went 9 minutes without a shot on net.
5) 3:57, Suzuki from behind the Leafs goal line threw the puck toward the Leafs goal as a centering attempt, instead it bounced off Kallgren's pads and immediately went out of the Leafs zone. Once again, this was very charitably considered a shot by the Toronto scorekeeper.
6: 0:52, With the Habs on the PP and their net empty they set up a one-timer for Hoffman. He gets it off but despite Montreal having 2 extra players on the ice there isn't a single red & white jersey anywhere within 8 feet of the Leafs crease and Kallgren is able to see the pass-then-shot the entire way and easily gets in front of it.
7: 0:07, similar to the Suzuki play Gallagher is at the corner of the rink on the Leafs goal line and passes it to the front of the net despite the fact that there is no Canadiens player within 15 feet of the net and it just bounces off Kallgren. Again, Toronto scorekeeper being very kind in considering that a shot on net.
So we have a period here where Montreal got 7 shots on goal. 3 of them would absolutely not be considered shots by any serious hockey individual. 1 of them was a very routine save any NHL goalie could make as well as most AHL goalies. 2 of them might have been decent scoring opportunities if Montreal had any bodies in front of Kallgren but they did not so he was able to stop those without much trouble. And one of them was yes a legitimately good scoring chance. Are you really going to sit here and say that because of one good scoring opportunity that Montreal "owned" the 3rd period?