From the date of that template, I expect it is using the original (v1.3.8) version of Column Grid, which is much simpler and has no sorting modifications from stock. So it is not really relevant to the issue. (It is compatible with v1.5.x, even though product_liating.php changed; the change was minor and it still functions as it used to.) I'll do some testing of mfr sort vs. list/grid sort to see if I can find a conflict.