Just to clarify that I'm reading this correctly and/or understanding it correctly - Godot has no shadow support for webgl currently?

Web export is still in development and officially was always a target for inclusion in 4.1 not 4.0. Luckily it had gotten far enough to be somewhat testable by the release of 4.0 so it was included early. You should expect there to be potential issues as well as missing features and yes, I believe shadows are currently one of those.

Yes, that is correct. There are no shadows in the OpenGL renderer on Godot 4.0, meaning for WebGL or mobile/desktop compatibility mode, they don't have realtime shadows.