The way I understand the design of this sticky header is that the assumption is made that when the person is trying to scroll up, he is trying to access the menu or navigation to perhaps go to another section in the site and to enhance to the user experience, the site provides the sticky menu as you highlighted
The menu is hidden when scrolling down since the focus is on the content and the menu would be a distraction but the quick access to the sticky menu (while scrolling up) allows for the user to quickly navigate without having to scroll all the way to the top.
To quote this smashing magazine article which did a research study on how users feel about sticky menus
STICKY MENUS ARE 22% QUICKER TO NAVIGATE
The data from the study indicated that participants were able to find what they were looking
for quicker when they didn’t have to scroll back to the top of the
page. 22% might not seem like a big number, but it can have a big
impact on visitors. According to this data, sticky navigation could
cut 36 seconds off of a five-minute visit to a website.
That said, as you pointed out sticky menus can be intrusive and distract the user as pointed out in the same article
DISTRACTING AND INTRUSIVE
If not done carefully, sticky navigation can be distracting. Some
sticky elements get delayed when bouncing back into position as the
user scrolls down the page. Others are so tall or wide that they
dominate the layout and impede access to the content. Navigation
should be easily accessible but should not compete with the content
for attention.
I couldnt find a name for this but this plugin allows you to create such a header