Why does fulltext search in SQL Server works better with an English index for non english content?

Question

I have the following query

SELECT  ct.Id,rankdegree FROM (SELECT c.[KEY] as ID ,c.[RANK] as rankdegree 
 FROM 
 CONTAINSTABLE( dbo.SearchItems,*,N'FORMSOF(INFLECTIONAL,хорошую)',1000) as c)  
 as ct where rankdegree>0

Table SearchItems contains some Russian text. "хорошую" is a russian adjective which means good.

So the problem is the following: if full-text index for SearchItems is build for English language the query returns results which can be qualified as suitable but it does not return anything when full-text index is build for Russian language.

Sql Server Version: Microsoft SQL Server Enterprise Edition Create Index Query:

CREATE FULLTEXT INDEX ON SearchItems
( 
  Title  Language 1033,
  Description Language 1033,
  FullData   Language 1033     
 ) 
KEY INDEX SearchItemsPrimaryKey;

for English and

CREATE FULLTEXT INDEX ON SearchItems
( 
  Title  Language 1049,
  Description Language 1049,
  FullData   Language 1049     
 ) 
KEY INDEX SearchItemsPrimaryKey;

for Russian