You're not annoying at all! It's confusing. This is my understanding from what they've told us:
Mixtapes are fully produced, written, etc by the members, and while they can request help from company employees it sounds like those employees get to choose to be involved and it's all pretty voluntary. The company staff will also assess it hold it to their usual standards but revisions fall on the artists as well. This work is done outside of the usual schedule.
So the point is it to be the free expression of the artists without the pressure but also without the full support that goes behind a full release that will have the usual promo, roll-out, physicals, etc
They also see these as a gift to fans, music that doesn't come with an expectation of purchase; their passion is music, making it and sharing it, and it separates the "BH - BTS style" and the member's personal expression
While free, they can still enter the billboard charts because of streaming numbers and itunes/them being placed on paid-music sites. (They do this because ARMY request it/WANT to pay for them) as well as MV views such as for Daechwita
BH will however gladly - and it sounds like of their own volition, Hobi was surprised there was going to be a full MV for Chicken Noodle Soup and it was such a big deal - support and pay for videos that I'm guessing they split the profit with the artist for. however, we're not aware of how that works exactly; Yoongi was able to turn Daechwita into the amazing thing we saw from what was supposedly a very simple initial idea. The vid was his concept. Did he pay to upgrade it, or did the co? Unsure. They're very very rich men now, so either is possible.
At times mix tape songs will get snapped up the company to become official releases, like Stay and Your Eyes Tell by Jungkook (he told us they were meant for his mixtape, so that's a reason for the delay/he needs new songs) were. This is good for the creating member, bc that means they'll make much much more money off those songs. Bang PD wanted Everythinggoes from Mono to be a BTS song but Namjoon said it was too personal and wanted it on his mixtape.
The Members themselves keep repeating that their focus is on BTS - the way they still only do brand sponsorships as 7 after their contract show that it's clearly a preference. Both them and BigHit could make MUCh more more money sending them out individually as well like other companies do, but they seem to have no interest in that or going solo. The solos they get on official releases appears to be their focus.
We'll see what happens in time! But yeah think of mixtapes as gifts, really, and the members sharing music just for music's sake with us.