> It doesn't matter if it uses less energy than cellular; it still uses ADDITIONAL energy.

This is not true, because both cellular and wifi connectivity do not have a fixed energy cost. That is determined by both utilization and reception quality.

When you are on WiFi with a smartphone, cellular utilization goes through the floor because nearly all utilization is moved to your more energy efficient wifi connection. Even more so if your carrier supports WiFi calling.

I can prove this in my own house. When I turn WiFi off on my phone for whatever reason and forget to turn it back on before the end of the day, my battery drains noticeably faster.

The things you say were true 15 years ago. But technology has changed and improved tremendously since then.