This, I believe, is very real - the Merck Exodus is beginning. Precisely because the pension formula, going forward, will no longer weight the years of service in the same way it has in the past, and also as the OP states, rising interest rates dramatically cut the value of lump sum payments.
HR may think this will be a great opportunity to reduce salary and benefits maintained on the books, which is potentially true, but this time I believe the magnitude of the impact has not been accounted for - and training of new employees is unfortunately, not a strength.
In any case - get out while the getting is good!....