If you enable log you would see that we send the g-code 1:1 so if it is the same as with octoprint it should get same height. Exception is if you have in server or octoprint different start g-codes or substitutions for homing or some G92 Zxxx that change Z. In 2d preview you see layer height - that is z send to printer per layer. Check layer height of last layer of gcode. If printer is calibrated correctly that would be the height you get. At least it is the height we send to printer for z. But any difference in homing z or bed leveling can add such a small difference easily.
