And those “brands” are, let me guess… Apple? Because the others do not have that (not counting their native apps). Literally no one. Instagram looks identical on Xiaomi (HyperOS), Samsung (One UI), and Nothing (Nothing OS). Same as WhatsApp, Telegram, YouTube, Netflix, Google Wallet, Soundcloud, VLC… you name it.
Pixel 11 PXL vs S25 Ultra:



All third party apps looks exactly the same on both phones (despite of their totally different UIs, so Pixel UI vs One UI). Because Google and Samsung do not develop those apps, they can’t “add transparency” to them. No one can but the devs of those apps.