So for a long time in ST I had a long time issue with HUE hub link.... when I shared a light that was a hue with Alexa it showed up twice in the Alexa Smart Home device section as both a HUE and ST device which annoyed me forever and ST refused to fix that.
Well today I removed Hue Hub from ST and added it to HE and guess what ?? No more double device listed in Alexa !!!
This was a hotly debated topic. Should we allow Hue devices to be discovered by Alexa or not, given that they can be discovered natively, we decided not to allow them to be visible to Alexa through Hubitat. It is extremely difficult to remove Hue bridge from Alexa once you have it paired, so we figured it was just easier for users to pair Hue directly and probably a better user experience as well.
This is definitely a nice convenience of Hubitat, but it's hardly a "bug" in SmartThings--Alexa is doing exactly what you told it to do if you have Hue devices discoverable via both the Hue Bridge/app itself and the ST Alexa SmartApp. ST can't "know" (nor does Hubitat) that you have Hue/Alexa integration already enabled, and the desired configuration in either case is to simply not select the same device twice (likely keeping the native Hue integration rather than going through ST or Hubitat, though you could do it either way).
That being said, I value this feature because my devices are scattered throughout the alphabetical list, I do want to use the native Hue/Alexa integration, and this makes it very easy to avoid problems.