Yep. Unless you're itching to see downtown Vancouver, the route up hwy15 through Cloverdale is easiest and fastest. You literally take two turns from Seattle to get to Whistler: one to get off I5 at...

That first post in the link is exactly how I would describe it, including the proper route. The only time I've done sub 4 hours is early in the morning. 10-15 minute border wait is typical.