So, 23 years instead of 24? Or 3.5 years instead of 3? Your correction without conclusion doesn’t seem helpful in deciding which calculation is least wrong.
It should be noted though that it is pretty rare to reach $175K salary in the GTA before turning 30 (Average household income in Toronto is sub $100K[3]). Therefore for the majority of people it will take more than 18 years to build up that down-payment, which could be where the number in the article came from.
[1] https://toronto.ctvnews.ca/average-gta-home-price-to-top-1-m.... [2] https://www.moneysense.ca/spend/real-estate/cmhc-tightens-mo... [3] https://www.toronto.ca/city-government/data-research-maps/to...