There are still risks associated with firm offers. Here is sample wording from one of Canada's top banks about their pre approval.
"Good day, Thank you for the application and support of our bank; pre-approval commitment is enclosed. RATE HOLD ONLY***Final approval is subject to meeting our bank's lending guidelines for property eligibility, credit history, employment income (with confirmation income is not impacted by COVID-19) and down payment verification before closing. "
Suppose you are buying with less than 20% down payment. Your applicancy may be strong as far as high ratio deals go, but one potential concern buying in a declining market is if the insurer perceives the price was too much and requires an appraisal AND if the appraisal comes in lower than purchase price. You may have no extra funds to cover such a shortfall. If you have at least 20% down payment AND you have a decent amount of extra $$ you could use if an appraisal comes up short, then you may be okay. By no means a sure thing though.
If you are offering with a condition of financing, 48 hours should suffice for us to find out where you stand. If no appraisal is required then we can be approved within 48 hours. If an appraisal is required they will tell us .....and an extension would be needed.