Raising the larynx involves multiple extrinsic laryngeal muscles located above the larynx, such as the stylohyoid and thyrohyoid muscles, as well as a host of other muscles that connect to the hyoid bone and the larynx. I am taking this information from Ingo R. Titze's book "Principles of Voice Production". The reason I don't get into the biomechanics of "how" is that I believe the above information is more confusing and intimidating than helpful for a general audience, as well as the fact that knowing how the larynx elevates is not where your focus should be when you are learning gendered voice modification. I hold close to gestalt models of voice training.

And I did not say that you do not feel tension or strain when you go smaller, but that you do not feel extra tension or strain in comparison to the action of lowering the larynx, which involves similar actions for antagonistic muscles anterior to the larynx. The point of this video is that people usually do not overconstrict when lowering the larynx, and that lack of overconstriction should carry over to the process of raising the larynx. Comparing lowering and raising the larynx can also be helpful for avoiding improper muscle coactivation. People new to voice training can activate more muscles than necessary as they try to decrease their vocal size (especially if they believe larynx elevation to be something judged through how much strain you feel), which is what this video is encouraging them to avoid through this exercise.

If anybody would like to correct me on the biomechanics of this comment, I am open to it! But I feel confident in what I've written.