Yes, that is the case unfortunately.
It's been mentioned in our FAQs for some time:
www.whitelabel.net /
serato.com
Mixed In Key rewrites a lot of MP3 tag data and, in the process, it can corrupt the high quality audio data stored in the Whitelabel audio file. Furthermore, I think it's safe to assume that the effectiveness of Mixed In Key is reduced somewhat with .wl.mp3 files because Mixed In Key will only read the lower quality audio portion of the file.
So, for now, we recommend you don't use Mixed In Key on Whitelabel audio files.
