The thing about these debates is that it turns out there's just varying shades of grey, nothing is black and white. Is Chicago's El a metro? It's heavy rail, frequent, yet not entirely grade seperated. How about Vienna's U6? It's entirely grade seperated, but uses low floor light rail vehicles. If it's a metro, then what's Ottawa's confederation line which is virtually identical in terms of rolling stock, grade seperation and capacity, but it's called LRT. The Canada line in Vancouver uses the same rolling stock as several asian metro systems, and the vehicles are as wide as a TR train, but because it's only two cars long is it a metro? If it's not, then what's Cincinnati's red line which is also only two cars long, yet generally considered a "real" metro. What about the shuttle lines on the NYC subway which are also 2 cars?
It's all just becomes very fuzzy, so arguing over the terminology goes nowhere. So instead a better comparison is how does the Montreal Metro + REM compare against all the planned lines of the TTC, which includes lines 5,6,7 and 8, even though all those are "LRT". I'd exclude Go RER since it's more regional than urban focused, but even that point is debatable.