There are three things I want to say about this.
One, I recently heard a bodybuilder say that muscles do not remember exercise variations and therefore using variations is silly.
About this, if we look at variations only from the perspective of muscles (a silly idea, imo) then any group of exercises which have overlapping muscles becomes a variation and therefore silly to do.
However, Exercise Variations should be looked at as movements separately and independently on their own - not that circular thinking way of "movements are caused by muscles and therefore muscles are the basics of movements so all you need to know is muscles".
Two, we use Exercise Variations extensively in our training because they do have their own unique added benefit. The general statements we read are true: a Snatch Grip Deadlift will help build a stronger upper back which will help in handling more weight overall on the Deadlift. Similarly, Pin Presses will help a trainee lift more on the Bench Press or OHP (if the Pin Presses are Overhead).
But, I think it is futile to try to quantify how much this added benefit is. Sometimes the co-relation is so indirect it can only be qualified through comfort in the lift and/or smoothness of the pull (which is also another deceptive factor btw). A lot of Percentage Based Programs explicitly state that if you can Rack Pull 110% of your 1RM then your Actual Deadlift is now at 102.5% or whatever arbitrary number. This is wrong because not everybody is the same and it is impossible to be able to predict a certain quantity every member of the general population can successfully attempt.
Three, I also heard someone mention that Exercise Variations are a form of progress. I think this is true and at the same time it is also untrue. In terms of unilateral movements - lunges, raised lunges, all the way to pistol squats are all progressions on exercise variations. Defining it as "similar movements", one can see how the epitome of single leg movements is the Pistol squat. But at the same time, I do not think that this is the same for Squats for example. Or Deadlifts. Or the Bench Press. The Pin Press is not a progression from the Bench Press. Perhaps this has to do with ROM though. For example, I think, going from Back Squats to Front Squats to Overhead Squats is actually a form of progression because the exercises get more and more technically inclined and less about "brute strength".
"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover."
"If you tell the truth, you don't have to remember anything."
"Never put off until tomorrow what you can do the day after tomorrow."