Neither the description here nor the README that comes with the files says that the WAV files are not intended for GB Studio. The README says that "some sound effects may sound different compared to the WAV files", but that's all. The description here says "The pack comes in .WAV, .VGM and Naked .VGM formats, These will only work on GB Studio 3.1 and above." which makes it sound like WAV is a supported format.