There is no such thing as absolutely necessary when it comes to lifting weights other than get plenty of sleep and squat.
Problem with most new lifter's is they either don't squat, squat like a candy ass or don't even train legs. I know because I was one of them 17 years ago when I first started training. I trained consistently for +3 almost 4 years then and did your classic high volume/high frequency lifting and did not train legs or do deadlifts at all. Needless to say that despite having pretty solid genetics I was severely short changed after the first 6 months of newbie gains.
Starting Strength is probably the best program any beginner can follow as it will teach you the basics and get you gaining strength in the core lifts rapidly.
When you are a beginner every thing you do in the gym will stimulate gains pretty much and because you are a beginner the weights you use even though they feel heavy at first will not significantly impact your recovery so you can train more frequently.
This is why you squat 2-3x a week in the beginning and bench 2x. Actually you can continue to train this way literally forever with adjustments to volume and intensity of the workouts. There is something to be said for always squatting 2-3 days a week. It's good for your neural pathways and helps keep technique as fresh as possible.
As you progress from beginner to intermediate the intensity of the workouts increases because you are lifting much heavier weight and can push yourself harder. This is why alot of people switch to the 1x a week body part training. Imo, this isn't ideal.
Concentrating workouts around a specific whole body lift with assistance exercises is great aka typical powerlifter template because it is in line with the stress-fatigue theory and the intermediate to advanced lifter's recovery ability, but specific body part splits like typical bodybuilders use is pretty unproductive and even counter=productive for the beginner and intermediate lifter who should really just focus on getting stronger on the basic compound lifts and eat and sleep an adequate amount to promote strength and weight gain.
For the beginner Starting Strength is probably the best bet.
Practical programming is an even more invaluable book because it will give a very solid, general understanding of how intense exercise impacts the body and how proper training should be structured to account for a lifter's progress from beginner-intermediate-advanced and beyond.
So many people try to train like and advanced lifter right from the get-go and don't understand that an advanced lifters has both an stronger recovery ability and requires a far greater stimulus to elicit strength/muscle gains while keeping withing his own recovery ability.
This is why a basic understanding of periodization is pretty crucial.