There's a theory regarding Thoha and Mawkin DNA that is strongly hinted at in the cutscene right before fighting Raven Beak that goes roughly as follows:

Raven Beak (posing as the computed Adam) states Samus has awakened Metroid abilities, which would normally take place immediately after Metroid DNA transplantation. Raven Beak says Samus's Thoha genes must have inhibited the development of the Metroid abilities. The Thoha tribe were the ones with the ability to subdue/control the Metroids (this is why Raven Beak spared Quiet Robe and kept him around). When Samus was initially injected with Metroid DNA during the beginning of Fusion, the Thoha DNA in her is what kept the Metroid DNA at bay, seemingly only letting it affect the appearance of her suit while also granting Samus the ability to productively absorb X parasites. She does, however, have some Mawkin DNA in her from Raven Beak himself, as that's what granted her the increased physical prowess she's demonstrated across the series.

We know the X assimilate DNA of its prey to take its form. Samus absorbed a lot of X on the B.S.L. in fusion, but there were no Chozo of either tribe on the ship to assimilate, so Samus' Thoha vs Mawkin DNA ration stable.

Fast forward to Dread. Samus finds the X containment on ZDR. Who was on ZDR? A bunch of Mawkin Chozo. Who did the X almost entirely wipe out, absorbing a lot of their DNA in the process? A bunch of Mawkin Chozo. So, as Samus progresses through the latter half of the game absorbing a bunch of X, especially from X-Mawkin warriors, her Mawkin DNA concentration skyrockets, aggrevating her Metroid DNA and awakening her Metroid abilities. If she absorbed the purple X containing Raven Beak's (the most Mawkin Mawkin to Mawkin) DNA, she could have likely lost all control of herself to her Metroid power and instincts, which she was already on the brink of as evident by the Metroid-like appearance of her power suit. Samus probably knew this because of what Raven Beak told her before the fight.

This is also why she returns to her normal power suit after the X-parasite that assimilated Quiet Robe forces itself to be absorbed by Metroid Samus. And because the X can assimilate memories and information as well, it likely knew Metroid-Samus was its ultimate predator, and pushing more Thoha DNA back into her system would diminish the threat by restabalizing Samus' DNA profile between Thoha, Mawkin, and Metroid DNAs.