Morinella was established by Meyer in 1810 for Tringa interpres Linnaeus 1875 alone, which Meyer (at the end of this footnote) suggested to rename Morinella collaris. The type of Morinella Meyer 1810 is thus, by monotypy, Morinella collaris Meyer 1810 = Tringa interpres Linnaeus 1758, which is the turnstone. The name can not be used for a group that would exclude this species.
In his 1812 Anmerkung, Bechstein referred to Meyer's footnote, which he merely paraphrased, citing characters that match turnstone better than upland sandpiper (bill shape, thick and short legs, short neck, etc.), and ending with a suggestion to change the name of the bird into precisely that which Meyer had offered for turnstone. There can be little doubt that this Anmerkung ended up where it is by accident, and was actually intended to be associated to the preceding species, which was indeed Tringa interpres Linnaeus.
If you insist that the Anmerkung must nevertheless be accepted as concerning Tringa longicauda, you might possibly construe it as having resulted in the creation of a genus-group name Morinella Bechstein 1812 (nec Meyer 1810) -- type, by monotypy, Morinella collaris Bechstein 1812 (nec Meyer 1810) = Tringa longicauda Bechstein 1812. But this name would then be a junior homonym of Morinella Meyer 1810, and a junior homonym cannot be used as the valid name of anything.