Pure speculation, but after the #501 wreck, Amtrak pledged to make Oregon and Washington whole (in stark contrast to the aftermath of the Cambers Bay #506 incident when Amtrak wrecked the train, and then told the state they would have to pay for Amtrak replacement equipment). The Chambers Bay wreck last July took an Oregon-owned set out of service, and this wreck nailed a Washington-owned set.
The two Wisconsin sets may have enough differences from the two Oregon sets that testing at Pueblo is needed. Rumor has it that the sets will then go back to Talgo in Milwaukee for some mods (maybe converting one or more cars to business class?), then out to the PNW to free conventional equipment, add the set needed for the additional round trip promised with the bypass and provide some margin for maintenance. As I said, pure speculation, but with the PNW short Talgos, and two sitting idle in Indiana for a couple of years and now moving around, it's possible to connect the dots.