Rate mismatches are much less of a problem with crystal-controlled receivers and transmitters at quite high rates, compared to the bad old days of mechanically-timed slow rates from teletypes and telex machines.
I agree, baud rate mismatch is sometimes misunderstood and given much more concern then it should. I repaired teletypes in the Air Force in the late 60s and even those old mechanical devices had quite of range for speed mismatch and still receive error free. As stated any character timing is reset on each and every start bit so mid bit sampling error will only accumulate for the length of data bits.
Lefty