This is true on newer vehicles. It certainly isn’t true on older models, and I prefer that the A/C not come on, unless I choose to turn it on. On a typical car from the 1980s to early 2000s, turning the HVAC to windshield or windshield/low level vents did nothing but move manually actuated dampers inside the dash, which direct airflow to the windshield and/or floor-directed vents.
It did not affect the temperature setting–which itself just controlled a manually-actuated blend door, and it certainly did not activate the A/C compressor.
Nowadays, turning the HVAC to those settings tells the BCM to move motorized dampers, and it also activates the A/C. As always, some people like the added convenience, others prefer the simpler more reliable design.