You're making an assumption about the percentage of financing. I've read a number of stories of boomers downsizing and/or putting in significant amounts to help their kids.
But I agree we don't have the data on this - so my anecdotal speculation is as good as yours.
I have a feeling that boomers won't be selling their houses and downsizing to condos en masse for a while, especially if their mortgages are paid off. There aren't a lot of new detached home lots being put up in Vancouver and condo prices are kept proportionally lower because the supply side for condos is much higher.
Boomers will repair/renovate/refinance their detached homes (with renovations done at the fraction of a condo purchase - financed by equity, and also increasing the resale value) and continue to live in them (possibly with family or extended family) for as long as possible while single-home lots appreciate in price.