I've gotten that message too.
I think maybe all long distance sleeper fares convert at ~.0289/point so just dividing the $ fare by .0289 will you a close enough # of points for comparing and planning.
NER trips otoh convert at ~.0223/point and that's based off the Value Fare which changes often.
FYI, nearly all Amtrak travel converts at $.0289855 cents per point. Including NER trips.
This is always based on quoted Value Fare, Business Class Fare, or Sleeper fare, *without* any discounts. (So if you qualify for one of the 10% discounts, like most of us do, you have to multiply that by .9, and find that it's worth $.0260866 ... But if you also have the credit card, the 5% points back on points redemptions means you have to divide by .95 and then it's worth $.0274600 -- and of course Saver Fares are always cheaper)
The exceptions are:
-- Acela, which is only $0.025 (so, never redeem for Acela)
-- non-NER business class often gets a slightly *better* conversion rate, closer to $.03
-- on the "blackout dates" points prices are jacked up
-- and of course, the weird issues wtih "call for price".
I found that the "connective discount fares" where A-B-C is cheaper than A-B + B-C don't seem to be that common, so I've taken to booking each leg independently except where I want Amtrak's guarantee of rescheduling in case a late train breaks a connection. It would be interesting to know which connections actually do offer "connective discount fares"; I may just habitually take connections which don't.