Everything you've read is not wrong, but it's used out of context. In most trainees with less than 5-10 years of training background and without an ass full of steroid needle tracks, muscular protein synthesis returns to baseline within 48 hours after a single bout of resistance training.
Exceptions exist, but they are rare.
It's why the Starting Strength model is far superior to body part splits for beginners and intermediaries. After a few years of training when you're closer to your genetic limit for strength and muscle size and you're interested in hypertrophy training as opposed to function, then a split program makes sense in context, since you're close enough to your genetic limit to need more training volume for a particular muscle group than what you can get in with 3xwhole-body; going to a push/pull or upper/lower 2xweekly for a total of 4 weekly sessions then makes sense.
But if you look at something like DC training, Westside Barbell, Bill Starr's 5x5 and a whole host of other models for very advanced athletes you'll see they're also using 3xweekly sessions just like starting strength, it's just that they're using weekly, monthly and even yearly periodization schemes to inch a little closer to their genetic max.
The bodybuilders you see in Muscle&Fiction and other magazines sure as heck didn't start out with a split routine and got anywhere; beginners shouldn't be looking at what advanced athletes are doing now after 10-20 years of consistent training, they should be looking at what that athlete did to get to that point in their training career.
Of course split routines work too, for a given value of work. It's just that they take longer and deliver less results than a whole-body routine performed 3xweekly for the novice, beginner and intermediate trainee. In my book, slower, inferior results isn't exactly worth recommending.
Context-dependent though. If you have a) 10+ year of lifting experience, and b) hypertrophy-oriented goals, body-part splits are a useful training methodology and will deliver superior results in that specific training parameter - for that specific population. Everyone else just aren't strong enough yet to be able to train with a high enough load to make body part splits a useful training modality.
(Body part splits are in general outdated as a training methodology even within bodybuilding, and it's certainly gotten a well-deserved kick out the door by most strength coaches. Push/pull-oriented workouts or movement-oriented workouts focused on basic compound exercises with assistance exercises to strengthen weak muscles in a particular kinetic chain deliver more results in less time.)
Interesting fact: did you know that adding an isolation movement to a compound movement that works the same set of muscles do not improve muscle growth? Once you've maximally stimulated muscular protein synthesis in your triceps by performing a set of close-grip bench press at 85% of your 1RM, the addition of triceps extensions or pressdowns won't lead to more muscle growth. Once you've done your chinups and rows, your biceps will have had all the stimulation they need to grow and adding more in the form of bicep curls won't make a meaningful contribution to your training.
Well, for a beginner, that is. A more advanced athlete may need more training volume to stimulate muscle growth if that's a goal for your training and there's a limit to how much heavy loading your joints can take which is where isolation and assistance exercises come in. And split routines, because getting in sufficient volume takes time and there's a limit to how long a meaningful hypertrophy workout is.
But even if your goal actually is bigger muscles, up until you have that base level of strength you'll have better long term results from focusing on mastering the basics.
If you're just starting out the best advice I can give you is to pick up a copy of Mark Rippetoes' Starting Strength book.
I've been doing this for a while and I still pick up on new things when I go back and read through it and "practical programming for strength training".
In other news, I'm trying a Pavel concept for my current workout - I'm "greasing the groove" on chinups. Legs seem to be more functional again after the surgery but with the layoff period I think I'm going to stick to bodyweight exercises for a week or two until I'm convinced everything works.
The combination of chinups, pushups, dips, and single-leg stepups doesn't cover everything of course. But it does help get prepped for more; I have remarkably little interest in crippling myself with DOMS if I can avoid it. Assuming no funny business from the leg, I'll be back under the bar squatting in a week or two ;)