I believe that Echo devices (such as Tap, Show, Dash Wand, Look, Fire TV & Fire Stick) are designed for specialized products to serve a specific purpose.
Respectfully I somewhat disagree, in my opinion the various Echo family models should have value differentiation based on hardware design not software compatibility.
The Original Echo has the best speakers for music, the Dot is small for easy placement, the Tap has a battery for flexible portability, the Wand a scanner for ease of shopping, etc. BUT if the device accepts voice commands, and/or has common hardware, then it should support all related available software features - It just makes good long term sense. For instance, and in particular for the "Calling & Messaging" feature, the larger the device community base the better for everyone. In the case of common hardware - Want to play music on the Wand, if it has a speaker, let the Customer decide with understanding of the trade-offs.
FWIW, I waited to purchase the Tap until the firmware allowed hands-free same as the other models. But most likely will return Tap if precluded from "Calling & Messaging". (And also worth noting, after a few days experimenting I'd say the Tap recognizes hands-free just fine, well across a room and multiple family voices without issue so I would think the microphone is entirely capable...)
Thanks for the reply,
Bob