There are way more than 12 statements generated. You get one statement for each year and month combination for each language where the first 3 characters of the month name are different.

Personally, I think you would be better off using a table naming scheme that is not locale dependent like
'Sales_' +
cast(datepart(yy, @PrmOrderDate) as char(4)) +
'_' +
cast(datepart(mm, @PrmOrderDate) as char(2))

To see the table names that you get now, run the following ...

DECLARE @PrmOrderDate DATETIME;
SET LANGUAGE N'us_english';
SET @PrmOrderDate = '01/31/2021'; -- set date here because the date literal format also depends on LANGUAGE
SELECT SUBSTRING(DATENAME(mm, @PrmOrderDate), 1, 3) + CAST(DATEPART(yy, @PrmOrderDate) AS CHAR(4)) + 'Sales';
SET LANGUAGE N'Español';
SELECT SUBSTRING(DATENAME(mm, @PrmOrderDate), 1, 3) + CAST(DATEPART(yy, @PrmOrderDate) AS CHAR(4)) + 'Sales';
SET LANGUAGE N'ελληνικά';
SELECT SUBSTRING(DATENAME(mm, @PrmOrderDate), 1, 3) + CAST(DATEPART(yy, @PrmOrderDate) AS CHAR(4)) + 'Sales';

…ql-transact-sql.md