Your point is true with regular WMA (not lossless). However, lossless WMA is transcoded to WAV above a certain bitrate, and as the WMA codec is closed source, there is no integer-only implementation AFAIK.
For ogg vorbis, or flac, and the likes however, chances are there’s a suitable codec working on the slug. IIRC flac to wav transcoding is currently working on the slug.