The station code for Vancouver, BC is VAC, not VAN. VAN is Vancouver, WA, across the Columbia from Portland, OR. There is plenty of rail service to VAN from SEA, 3 Cascades, plus the Coast Starlight.
The Saver fare SEA-VAC was in the neighborhood of $25-30, IIRC, but there are much more reliable ways to tell a bus from a train than trying to infer it from the fare.
A train will have a train icon, a bus a bus icon on the reservation page.
A Cascades train will have a 3 digit 5xx number, likely 516 for the northbound train and 519 for the southbound train that have the best chance of resuming first. A bus will have a 4 digit 8xxx number.
Finally there is no rail service to Vancouver loaded into the reservation system currently for any dates at all, right through the end of released inventory 11 months out. Everything to Vancouver, BC on Amtrak.com right now will be a bus.
Per Amtrak's May 6th letter to WSDOT and ODOT, the sponsors and funding source for the services, service to Vancouver is not expected to resume until December 2022. I would not expected trains to be loaded into the reservation system until operating plans for service resumption are firm.