Yes - if a billionaire borrower buys a $200,000 house with a mortgage, there is little repayment risk for both borrower and banks. The mortgage payments are unlikely to stress the borrower.
No - that risk can be distributed between bank and borrower. Bank provides 75% of the value of the house, so it takes more risk. However, it can reduce risk in variety of ways, including: 1) taking collateral, 2) taking a guarantee from borrower, 3) diversification, 4) off loading risk to 3rd parties.
And if there's a crisis large enough that solvency of CMHC might be questionable, they don't have to worry either because the bank of Canada will gladly buy their mortgages, passing the risk onto taxpayers.
