Thank you for your report!
On one hand looks like you are right. But on other the page says scale should be nonzero in both cases, and that makes both values not fitting your case 
"SQL_TRUE if the column has a fixed precision and nonzero scale that are data source-specific.
SQL_FALSE if the column does not have a fixed precision and nonzero scale that are data source-specific."
But yeah, we will fix this.
Connector returned wrong value for SQL_DESC_FIXED_PREC_SCALE. In the
report it was going about bigint type, but in fact for more types
SQL_TRUE was returned, where it shouldn't. Since defininition of SQL_DESC_FIXED_PREC_SCALE is not super clear, I checked what SQL Server driver returns for different types. As as being also MS's creation, I guess it can be used for reference if specs
are ambiguous. Only (small)money types SQL_TRUE is returned. MariaDB does not
have it. And for types that has counterpart in MariaDB, SQL_FALSE is
always returned. Thus, i made SQL_FALSE default value for all types for
SQL_DESC_FIXED_PREC_SCALE field.