This name is a synonym of Betula platyphylla subsp. mandshurica (Regel) Kitag..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 21588) with original publication details: Cycl. Amer. Hort. 1: 159 1900.
This name was in version 1 of The Plant List, record kew-21588, and has not been changed.