Actually no. When you're learning a piece from scratch, you start with 60bpm or slower and slowly polish your performance and reach to the normal speed of the piece. If you're going to perform with an orchestra, you also rehearse a lot. We started 14 weeks before the actual concert date (used to play double bass in a symphony).
Learning the instrument is akin to learning the programming language. Music theory is the same thing as programming languages / intro to computation courses. You pass through them once and revisit as needed. Not everyday.
However, when you finish a piece, 95% of the skill required to play it again is permanent. You just rehearse it a couple of times and, viola. The performance is there.
The constant exercise part is very on par with what programmers do every day. You either code (work) or playfight/practice (hobby projects). Also, composers and genres have similar structures in their pieces, so when you get used to them, you can just fly through them, even if you play for the first time.
There are a couple of comments which say that we're talking about senior programmers here. Senior musicians can play what they see in the first pass, or just improvise/remix what they hear for the first time (see [0]).
So, in most cases, the partitions in front of the musicians are cheat sheets. I remember just looking at the section and playing half (sometimes most) of it without even looking to it.
The live/improvised performance is akin to "hacking" in programming. I had my mentor who taught me playing double bass had to improvise a bridge section of a piece because he forgot that specific part. He said that since he knows the motifs, he bridged the part on the fly, in a solo performance in conservatory, and he got a pass because how he handled it. This is how we hack something together when we're in a rough spot and dig our way out of it by knowing what we're doing, but improvising and trusting the process.
So, I draw these conclusions from 10+ years of live concerts and 15+ years of professional sysadmin/programming/research work.
[0]: https://www.youtube.com/watch?v=3pYHCGYJbw0