Will a glass bed warp as it is heated?
TL;DR
Yes, glass warps when hot. Use a physical touch sensor and calibrate it out, or swap glass if it's &quot;bad&quot;.

The further you go into mechanical studies like 3d printing, mills, and lathes, you will find out that nothing is perfectly flat. Everything has a tolerance to it, whether the manufacturer provided it or not. Better manufacturers provide the tolerance data.
As you have or will find out, yes, glass does warp when heated. That is because you are not warming the glass evenly. When hot and cold spots form in glass, the glass tends to warp up or down, depending how the heat travels.
It's common for 0.01 mm warp when a glass bed is brought to printing temps (60-100 °C). If one has a larger format bed, like my Vulcanus at 500x500, 0.03 mm changes are possible.
One can remediate this warping, as it usually appears in the same place during the heat cycle. So if you calibrate after the bed is heated, you should reduce said errors. Another more comprehensive way to fix this, is with a physical touch sensor and create a grid map of the bed geometry.