Yes. When Amtrak first started, they were still under the same ICC regulations as their railroad predecessors and all tariffs had to be filed. At that time the airlines were in same situation and their fares had to filed and approved by the CAB. It was the same cost for the same trip whether you bought the ticket months in advance or walked up that day, or whether travel was the Wednesday before Thanksgiving or in the depths of mid-February. Since then both air and rail fares were deregulated. Airfares were first. I am not sure of the timeframe for Amtrak but the yield management system was in place in the 1990s, IIRC.
Amtrak still is not quite so dizzying in their yield management as the airlines, but they have gotten more sophisticated with it over the years. Up until a few years ago, they did routinely allocate inventory into the lowest bucket when inventory was released 11 months in advance. They no longer do that and the old 11 month "rule" to get cheap fares is now a thing of the past. Amtrak now allocates that initial inventory according to historical trends and anticipated demand for the date with an "optimistic" skew towards higher buckets. They adjust inventory allocation among the yield management buckets as demand develops or doesn't.
They certainly appear to be on the "optimistic" (higher bucket) side right now for much of 2022.
Yield management isn't going anywhere. It is a way of life now. I have no intrinsic argument with yield management as long as it is done well. Amtrak is entitled to get what they can get for inventory that is both limited and perishable. My issues would be if it were done incompetently and inventory were allowed to go out empty because pricing was too high, or BidUp put that inventory out a fire sale rates after staying at high prices for too long. Based on reports here and on Facebook, BidUp is not resulting in really deep discounts thus far.
PS, VIA Rail Canada does not appear to be doing yield management, other than the amount inventory allocated into their "Discount" fare class. They have 3 basic fare seasons, Peak, Shoulder and Off Peak, each with a Discount and Full fare. They do (or did, pre-COVID) what amounted to distressed inventory sales with travel between selected points on selected dates released 4-8 weeks in advance which would be 40-50% off, but you could not plan around them since it didn't become available until relatively shortly before departure and there was no way to tell if your travel dates, destinations, or accommodation type would be offered.