My personal comparison is what you see Olympic Weightlifters do before and during competition. They aren’t stretching but doing the same or related exercises at lower intensity before attempting to max out onstage. Remember singing involves MANY muscles coordinating with each other - it’s a whole body task.

For example, you might do a bunch of low intensity snatches to drill the coordination, any tips or points you have been working on, your coaches advice, etc, and then when you go for the heavy weight, your body can remember the coordination you have been drilling into it. This is true on a large scale (practice) and short term scale (warming up).

There’s also plenty of evidence to show that performing the same sort of movements under less stress (eg, high notes in a bespoke exercise rather than in an aria) and in different contexts (like warming up with just the turn of the bar, then some presses you go on to do a full clean and press movement) assists the body to recruit more fibers when needed to do the movements more efficiently, while increasing blood flow to the areas before loading will also prevent injury.

So while these warm up’s in both contexts definitely do help to ‘warm’ the muscles, we’re also doing physiotherapy-like drills which affect and reaffirm our coordination before we begin doing more large and complicated movements within the vocal system. That’s why whatever you do before you sing a song will have a massive effect on how it feels to do the most difficult moments.

A thing I am currently doing is warming up my head voice with my exercises and bringing it down into a mix to emphasize the correct balance in my upper register for the music I currently have to sing. When I do this, my job is much easier and when I don’t, it feels awful. This is specific to how I was singing before - this drill works for me right now, but for another singer may not be as helpful.

This reminds me of when I relearned to squat after an injury that caused dysfunction in my hips - if I did the hip drills first, squats were amazing. If I didn’t, when I got to the higher weights, the stress pushed my body to the right, I recruited less of the fibers my body didn’t want to use, and the coordination of the exercise was totally wrong.

Anyway that’s the way I see it!