I don't think you're correct.
Lyman 49th using the same 240grn RNFP (Lyman #429667) states the OAL at 1.500" for its use in .44spl however, the OAL stated for .44mag is 1.645".
The SAAMI spec (from Quickload) for the cases in .44spl is 1.153" where as .44mag it is 1.275".
This is further corroborated by Quickload that lists the capacity of a .44mag case as 2.565 cubic cm.... yet for a .44spl case it lists 2.273 cubic cm.