WAV files are so old that there was never a schema developed for them to hold metadata internally. FLAC is merely a "container" for the WAV files having more robust places in the design (schema) to hold metadata, things like track name, number, and yes, cover art. Even lowly mp3 files have by design, places to put that data. If your streamer is working right, it will use the metadata but there should not be any sound artifacts from that metadata being present because they are not INSIDE the WAV file that is decoded. Free LOSSLESS Audio Codec is the nature of the beast. The same can be said for Apple's ALAC. I've encoded wav files as level 8 FLAC (the best compression that can be done and still be lossless when decoded) and level 0 (no mathematical compression at all) and can hear no difference in my headphones. But then I'm 65. Still, by design, these things should have no sonic difference at all. Even whatever chips were in a lowly 1998 PC could handle the decoding without issue, let alone modern, much faster chips in phones, and well-designed streamers.
Why do Wav and Flac Files Sound Different?
This article is from 2016, so outfits like JRiver may have developed workarounds for the metadata/sound quality issues sussed out below. Inquiring minds want to know.
Why Do WAV And FLAC Files Sound Different?
"Based on these results, we attempted to pinpoint which section of the metadata might be responsible. Since the cover art file associated with the metadata is the largest contributor to the metadata header size, we began by examining the effect of deleting cover art prior to the WAV-to-FLAC-to-WAV conversion protocol. This proved fortuitous, as our first suspicion proved correct."