The bare bulb sends light in a way that fills the modifier. This is what most modifiers are designed for. You can think of it as behaving somewhat like a bare lightbulb.
Speedlights are tiny and have to be designed to take maximum advantage of the (relatively) minimal amount of light their combination of tube and capacitors is capable of generating. The way this design works is that there is a focused reflector designed to send as much light forward. In front of the tube and reflector is a fresnel type lens which is designed to focus the light forward. This is, in effect, more like a spot light or a flashlight.
So, if you imagine you have hung up a sheet between you and your subject and you pull out a focused flashlight and shine it at the sheet, you will have a fairly small circle on the sheet and you can imagine the light will be brighter in the center. Now try the same with your lightbulb and the sheet will be more evenly illuminated. Now imagine if you aim your flashlight at an angle so the circle becomes a bigger shape.
Feathering the perfectly filled light modifier at the subject will generally give you a more flattering light. If the modifier is less perfectly filled, feathering helps even more.
Makeup with oil will exacerbate the problem with a specular highlight.
I did feather to the best of my ability. at no point did I directly aim the modifier at the subject.... always above them. I need to practice more and use the right light source