This term is not to be confused/doesn't have any relations with "Semi-Bisexual."
Also known as "Media-Bisexual" ("Media" stands for "half" in spanish,) is a term where an individual considers themself bisexual but may have less attraction sexually, romantically, aesthetically, etc to one of the genders. They are still willing to have a relationships/feelings for, and might have even have visualize themselves in a relationship with someone of that gender.
Due to fear, discomfort of sorts, or any feeling that makes the individual be hesitant to be in a relationship with/have feelings for said gender might have been caused by household environment, homophobia, dysphoria, trauma, etc, varying from person to person, and might not even be the primary source as to why.
One more factor being, that not everyone who identifies as "bisexual" might not feel comfortable/that terms like "bisexual gay (Bi-vincian/lesbian)", "Biromantic" combined terms, etc, don't fit, but just like that, hemi/media-bisexual can be combined with other terms.
History
This term and the flag(s) was coined on the 8th of June, 2021, by discord/wiki user, Musephile.
The flag remix and a more cooler tone from the original bisexual flag, the cooler tone and noise filter indicating the "feeling of hesitation of sorts" and along the "desire of wanting to be open about it."
Resource
https://discord.com/channels/718096257507131523/718281009774198814/851748206269956096