A quick inspection of the FT70 firmware package from Yaesu shows this is a Renesas microcontroller with a native USB port. In this case it emulates a serial port directly in firmware, rather than a separate USB-serial bridge chip. That's probably a first for an HT, but it's pretty common in the wider microcontroller world.
Yeah, I meant it'd be the first time I saw an HT that didn't just have a USB-serial bridge chip in it, despite appearing to have "native USB".
On devices like that, they just absorb the baud rate changes and pretend to be running at that rate, but it's a no-op inside the microcontroller. Because of this, the actual data rate over the wire can be much faster, since it's only limited by USB data rate and microcontroller speed.
Nicolas, I wouldn't worry about the baud rate changes; just leave it how it was and it should work fine and operate at max throughput regardless. However, changing it also shouldn't cause issues.
Agreed, especially if this is a reading problem and not a writing one, I wouldn't expect it to matter for stability.
--Dan