Not a must.
Basically the COS is prepared by OC and CO just signs it.
My unit my company, my OC is very particular about ppl getting
outstanding and he made sure he wrote testimonials to those he gave
outstanding. Basically all the men under him who attained "maximum
possible NSF rank" (e.g. 2SG, LTA) will get Outstanding. But those
who ord with "normal" rank (3sg and below) he just gives Very Good
unless there was a charge.
But another company's OC, just gave everyone Outstanding without
testimonials.
