Can you attach a screen shot of the issue please?

There’s normally a progress bar on the ‘Now Playing’ screen (it usually appears when you tap the album art image), but I don’t think there is the option to scrub on some services, (that’s from my own experience of using Deezer & Amazon Music), but there is an option to skip forward/backwards.

Example from Mac Sonos app.  Notice the song started from Alexa is missing scrub bar whereas the one started from with in the Sonos app has the scrub bar.

It depends on the feed within the service, at least with Deezer. Explicitly selected music should have a scrubber bar. ‘Flow’, ‘mixes’ or ‘stations’ -- and Alexa selected music -- tend not to. 

Same thing here with Sonos on the iPhone.  Stream started from Alexa = no scrub bar.  Stream started from Sonos = scrub bar.  Same service bvoth times, Apple Music.  The same thing happens with Spotify.

This makes sense.  Because notice the rewind buttom is missing on the one started from Alexa but its there on the one started in the Sonos app.

I think you can ask Alexa to scrub forward or backward by a time period (30 seconds for example).

"Alexa go forward/back by 30 seconds” - maybe it’s assumed we will use that method instead when using voice control to begin playback?

Could be.  It seems its behaving more like a radio station.  Of course when you are paying for a service the conbcept that you hgave limited FF’s and RW’s seems a bit weird.  But thats true across all paid streaming services.