Nintendo won't make that mistake again on burnt disc loading as they fixed it in later hardware reversions of the wii
You probably need to burn a specific optical media in a spceific way to make it to be recognized byt the console; in the old Wii old optical readers firmware was able to support the command set to read "normal" CDs/DVDs (so you can also use old Wiis to read CDs/DVDs) while in later firmware N removed the support to those commands making "backup discs" unreadable by the reader itself; they probably did the same in the SATA WiiU optical drive (yes, it should be a "normal" SATA drive with a custom connector; I know someone connected it to a PC using a custom made adapter but no other infos available).