Exhibit A:
Unmodified wiis are only able to read gamecube discs at 3x, meaning the absolute minimum time required for cleanrip to process a gamecube disc is around 550 seconds - I've tested this many times on several different wiis, because I wanted cleanrip's ETA calculation to be accurate. If it completed in 421 seconds the disc must be being read at a higher rate which is only possible if a modchip overrides the 3x restriction in the drive's firmware.
Exhibit B:
Filename: G8ME01
Internal Name: Paper Mario
MD5: BBFB80DBFE1D5FF80E0F2FBAB46DF0C9
SHA-1: 0321FE7407BDC6A609C2C4E75D4D4F0BDCEA6CDC
The dump completed but doesn't match known records for this game, indicating read errors. It's impossible for an unmodified drive to make mistakes while reading without detecting it; standard DVDs include error detection/correction data and wii discs are no different in this regard. If a disc had read errors, an unmodified drive would return an error code and cleanrip would abort. Modchips however will retry bad reads a couple of times and then just return whatever they managed to pull from the drive without signalling any error code, since this masks common read errors when using burnable media.