WOW! The great majority of my heels are 4" or 10 cm. I have a few 3" or 8 cm. I also have a couple pair of 5" or 12.5 cm that I struggle with. Now I will admit I would not want to walk very far in 4" heels, I certainly would not go shopping in them, but I see no issues hopping a cab or Uber and getting dropped of near the door of my destination. 3" I believe I could wear for an extended time. I do have a pair of block heel boots that are around 3 1/2" that I have worn while shopping. Stilettos would be a bit more to endure. 2"?? All day long baby! Regular every day height in boots.
I have to wonder about the author. Did she wear nothing but flats for the last few years? If yes, I would say there are very few people that could dive into a pair of 3" heels and wear them for an extended time comfortably after a long hiatus. 4" would be a big no, but buy a pair, wear them around the home, get the muscles and tendons stretched out again.
My first stiletto heels were 3". I thought the calf muscles in my legs were going to explode! I got used to them then bought 4" heels, same deal, calf muscles cramped up and got very sore in a few minutes. Today I wear 4" around the home all day with no issues.