MicroSD cards - about the size of a fingernail - absolutely come in sizes up to 1TB, that's not controversial or dodgy brands selling fakes. There's many brands selling cards at 512GB, ten times your BluRay example.
Portable flash drives using M.2 drives internally could reasonably be up to 8TB, but being at the high end they're expensive.
Samsung is a reputable brand that makes 256 GB and 512 GB SD cards (EVO Plus) - I have good experience with using it in Raspberry Pi. And "thumb drives" - USB sticks absolutely go into TBs - I'm using a 2 TB one, and I've seen colleagues use bigger. And you can put a modern M.2 NVMe SSD into USB-C casing and it's half the size of an old portable SSD...
It’s maybe a bit big to call it a “thumb drive” but I’ve been putting backups on a 2TB usb “portable ssd”. I’ve also got a 256GB thumb drive, which isn’t too far off.
I don’t think those are actually several TB. They’re fakes that are advertised as having several TB.