Model Advisory Warning For Selector block

I have used Selctor block to select data from 6 x1 array and Index signal to selector is of Enumeration type.

as per Selector block description , it support index signal of Enumeration type. but while performing model Advisory check I am getting warning that blocks have inappropriate datatype. when I used datatype convesrion block for index signal, it solves issue, But I dont want to use Data covserion.

Does any one knows why I am getting this warning as Index signal is supported with Enumeration type?