You are correct. General introduction of inventory at low bucket 11 months out has been gone for several years now as Amtrak has gotten more sophisticated in their yield management.
It doesn't hurt to look at prices at 11 months out, but do not be surprised if they are in the highest 2 buckets for sleepers, especially in peak travel periods when initially released. If demand doesn't develop, they will reallocate some inventory into lower buckets, however my spot checking seems to indicate they usually do not touch anything for at least 4 to 5 months after initial inventory release at 11 months.
My advice is not to book at 11 months, but rather monitor prices for a planned trip, have a flexible travel window and grab the first reasonable fare that shows up in your travel window (middle bucket for peak periods, lower for off peak). Then construct the rest of your trip around those lower fare dates.
Finally, everything I just said applies to sleepers only. Coach fares do seem to open at low bucket.