To me this subject isn't that difficult. It is all in the simplicity, and we sometimes make this far too complicated.
Each of us, whether we have lifting goals or not have certain dietary needs in calories, macro-nutrients, micro-nutrients, etc, "regardless" of the activity level of the individual person.
However, this basic need in calories, macro-nutrients, micro-nutrients (etc), can go up or down dependent on the activities of the person...and the persons' individual particulars (and the variable swings in weight disposition). Just because we are more active or applying a different method of stimulus, doesn't change the basics, it just increases them to a certain extent (dependent).
Like most things, it boils down to basic dietary mechanics---and to a degree some individual preferences that adheres to the goal desired (if one), and one's lifestyle disposition.
Here is an example: Person A is is wanting to lose tissue, which will assume a "basic" calorie restriction of 500c from Maintenance--to assist in soliciting this tissue loss.
In a deficit calorie environment protein can be drastically important (because of calorie depravity) and sometimes hard to fit in (but this can depend on the starting position of the person--weight/age wise). It can be also difficult for some to fit in protein because of lifestyle (like the kind of work they do and hours performed, for example). And, some just plainly do better with harder food items, then drinking some of their calories.
Two things are important here (pointing to protein, as subject matter): 1. Eating hard protein takes longer to digest and makes the body work harder (because of the longer digestive properties), 2. Supplementing with Whey Powder, is useful to hit protein targets and can aide an active person at work, but at the same time, the liquid properties digest and empty the stomach faster, which then a "combination" of food is another focal point of consideration.
My point here in this simple illustration, is to point out that if a person can fit in their protein (in hard food--hopefully a good choice variety), there is simply nothing wrong with it. And, if a person can progress by consuming both hard protein items and whey protein, there is nothing wrong with it (I wont get into pre and post workout eating and timing, this is just another individual subject matter to address on a personal level--dependent on many independent factors).
After losing 40+ unwanted lbs: