I don't consider two of those to be good comparisons to mass shootings of the "kill dozens of people in a couple minutes" variety.

The Saskatchewan stabbings were attacks at 13 separate locations across a sparsely populated reservation rather than a single mass casualty event.

The Sagamihara stabbings were attacks on sleeping disabled patients inside a care home. It reminds me more of Angel of Death type mass killings (by nurses / doctors). He considered it to be euthanasia and the weapon could have been a pillow - the mass killing was not down to the deadliness of the weapon but the passivity of the victims.

The Anqing attack is a better example - a single event against conscious victims. Nevertheless, mass stabbings across the whole globe are rarer than the daily mass shootings in the US.

The person you replied to said

"A person with a few full magazines and a semiauto rifle in a crowded place, and not much concern about surviving, can kill dozens of people in a couple minutes before there's any chance of someone else with a gun being able to stop them. I'm not aware of someone doing this with a knife.

The Canadian incident took place over days and 13 different locations. The other two incidents don't say how long they took but it just takes way longer to kill people with a knife than a gun.