Reading on the Web , seems that cloudfront streams have this issue but i have same problem also with another channels.. I've tested also directly in VLC and there is same switching of resolution .
Here is a Free Music List and You can try with Trace channels or Stingray for example that are native in 1920x1080 but starts in Low Resolution and switching to HD or FHD after ( same issue in VLC for Windows ) . If you need i have also A Distro List
https://iptv-org.github.io/iptv/categories/music.m3u
I Think that is a VLC Issue because i've tested in KMplayer and starts directly in FHD.
I've used ProgDVB engine for years and i Love it, i've changed Engine only because the orginal engine ramains in Low resolution in a lot of channels and not change automatic like Lib VLC ( sometimes not streams )
This issue there is also in Android, same channels streams in SD and changing engine not solve the problem . I've tested also another Android App that use Exo Player and stream directly in HD or FHD. Changing Preferred player in Exo in ProgTV Android seems not solve the problem.
I've asked for viewing resolution in OSD also in lib VLC for this reason. If You need i can test in Windows and Android any change