That's correct, you still need the SD-Card with the boot partition. I haven't found any way so far to modify that behaviour.
I was using the Adafruit micro SD card as well as an high class Sandisk one... had problems with both after a while. I took care about a proper power supply, always shutting the Pi correctly down and so on... nothing helped. After the third time this happened something had to change.
By the way, your absolutely not save on an Arduino with these things: A SD-Card is nothing more than some stupid memory, there's not really anthing intelligent on these things preventing them from data corruption (improper power down, power down during write and so on...). The "Secure" in "SD" only stands for one part of the memory where some DRM stuff can be saved.
Windows is also not really able to handle "broken" SD-Cards, it's always a mess to get them going after something went wrong.
The story in cams and players is a fairly simple one: These things just simply give a s*** about the file integrity. If you format a card in a camera it just replaces whatever there is on the card with a plain partition and it's structure (there's an Arduino sketch that does exactly the same by the way). Since most of these devices have a "Soft Power Off" the controller inside can finish any pending access to the card without any issues.
Back to that USB story: It needs some more power for sure, in exchange you get a much more reliable solution and it speeds up things quite significantly