On the Depth Chart page, just below the order of player substitution at each position (where you drag them) it says
"NOTE - The rating below the player name is for the depth chart position, not for the player's primary position"

I have never noticed any change in those numbers, A guy listed at two different positions has the same number at both positions. Does that sentence have any meaning at all, or has whatever it refers to been disabled? Thanks.

I think this probably refers to using player roles for player rating, which you can set and use from settings, if you want your overall ratings to be more customized to how you think the attributes are weighted. Doesn’t seem to make any difference with standard player ratings.