bug report: use case of vector reflect()

mySketch
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// This is a simplification of a real encounter of a bug in p5's reflect() 
// https://github.com/processing/p5.js/issues/7088
// In it, the calculation of the repositioning for ball bounce is 
// thrown off by the alteration of the passed surface normal by p5's reflect function.
​
let balls;
​
function setup() {
  createCanvas(windowWidth, windowHeight);
  createBalls()
}
​
function draw() {
  background(100);
  for (const ball of balls) {
    drawBall(ball)
  }
  for (const ball of balls) {
    updateBall(ball);
  }
}
​
function createBalls() {
  balls = [{
      pos: createVector(200, 200),
      radius: 200,
      vel: createVector(10, 2)
    },
    {
      pos: createVector(850, 250),
      radius: 100,
      vel: createVector(-4, 0)
    }
  ];
}
​
function drawBall(ball) {
  push()
  translate(ball.pos)
  circle(0, 0, ball.radius * 2);
  pop()
}
​
function updateBall(ball) {
  ball.pos.add(ball.vel);
​
  for (const otherBall of balls) {
    if (otherBall === ball) {
      continue;
    }
    if (otherBall.pos.dist(ball.pos) < ball.radius + otherBall.radius) {
      bounceOff(ball, otherBall)
    }
  }
}
/**
* Bounces ballA off ballB, changing ballA's course and repositioning ballA to stop intersection.  
* Doesn't modify ballB.
*/
function bounceOff(ballA, ballB) {
  //Adjust course
  const normalizedBToA = p5.Vector.sub(ballA.pos, ballB.pos).normalize();
  ballA.vel.reflect(normalizedBToA);
  // The behaviour can be fixed by replacing the above as follows: 
  // ballA.vel.reflect(normalizedBToA.copy());
  // This will work around the bug in reflect(), which mutates this normal.
​
  //Reposition out to touching distance, ceasing intersection
  const touchingDistance = ballA.radius + ballB.radius;
  const offsetPosition = normalizedBToA.mult(touchingDistance);
  const myNewPos = p5.Vector.add(ballB.pos, offsetPosition);
  ballA.pos.set(myNewPos);
}