As it says in the article, and as you indicate above, Electrify, the debate seems to be being waged over the usage of the word "subway". It's easy to infer, given that the mayor himself doesn't know that LRTs aren't streetcars, from comments online from people who don't know the LRT is grade separated, and what we know generally about the ignorance of the average voter, that the people in Scarborough who the mayor is supposedly listening to in large part hear the prestige and sophistication in the word "subways" and merely want the sexy option over the uncool LRT. It's like a child pestering a parent for some brand name this or that when the cheaper substitute will do just fine.
The fact-based arguments for the subway are laughable justifications for an extra billion-odd dollars in spending. Then there are the sunk costs and the time lost.
But people can keep pretending that walking down a flight of stairs is worth all that when pressed to make an argument, while obscuring the suitability of the LRT to the ignorant public with intentionally misleading sloganeering.