You're quite correct.
It's confusing, because Ottawa's Line 2 opened nearly two decades before Line 1. But it makes sense contextually.
Line 1 was a purpose-built transit corridor, featuring a tunnel through downtown and then broadly following a former busway into the suburbs at either end. It was designed to replace more than a thouand daily bus trips, with the entire bus network re-engineered around it, and most stations outside the downtown core having off-street bus bays. It is meant to be the spine of a growing transit network, fully integrated with other services.
Line 2 was the cheapest possible project that could plausibly be called a "rail pilot". It is a converted freight corridor, and it does not serve downtown Ottawa: in fact, before its recent expansion, the only major destinations it served were Carleton University and the large South Keys strip mall. There was no effort at bus integration except where the line already met the Transitway, many of the stations
basically amounted to bus stops, and several portions of the line were single-tracked, forcing it to operate with 15-minute headways. Which is to say, hardly anybody used it, except for people who lived near stations and wanted to go to Carleton or the mall.
When Line 1 opened, Line 2 became much more useful by virtue of connecting: you could now reach Carleton and South Keys from downtown with a single off-street transfer. Line 4, which connects Line 2 to the Ottawa Airport, makes it even more useful, although with two transfers, this service is notably slower than the direct bus that used to run out of downtown. And double-tracking of the line now makes more useful headways practical, which has made it more generally attractive.
Of course, clever readers will have noticed that this means Line 4 has opened before Line 3, which does rather make this all more confusing. But that's what you get with OC Transpo.