That seems fine for testing.
MAGMA doesn't do anything to detect or prevent faults from bit flips. If the bit happens to be low-order (like 0.00000001), then the difference will be negligible, but if the bit happens to be high-order (like 1.) or an exponent bit, the error is likely to be significant.
There are fault detecting & tolerant linear algebra algorithms, we just haven't implemented them in MAGMA.
Note that ECC memory normally protects against single bit flips, so what you are doing would correspond to a double bit flip that the hardware was unable to correct, or using non-ECC memory (gaming GPUs generally use non-ECC memory).
-mark