Not really. A shape like this makes your hands curl upwards when using the keyboard, so the tendons on the upper side of your hands are constantly in a tensioned position.
If you look at older thinkpads, (x300/301, x201 - x230, t410-t430), the keyboard was slightly recessed downwards or level with the palmrest, producing a flat typing surface, so the hands would rest on the palmrest in a slightly more relaxed position than the macbook conical shape.
Here’s some research on negative tilt angle keyboards:
The USB-C port for charging can be rather problematic, since this standard negotiates the charging parameters with the charger. It requires a chip on both sides, so simply delivering voltage to the pins won’t charge the device, and you won’t be able to use generic chargers that deliver proper voltage and amps. You’ll also run into issues of only one USB-C port being available for charging, displayport compatibility issues, and so on. Wacom has made this exact move in their Mobile Studio tablets, and a lot of users report this as having issues.
I’m writing this more as an anecdote. I imagine Purism does their marketing research well, and includes features that are a common denominator for the biggest part of their userbase.
About the palm rest area. I haven’t heard about the negative tilt on the keyboards before. But in my experince (#anecdotalevidence), It’s more comfortable to have keyboard (laptop) slightly up and not horizontal. When the laptop is horizontal, I tend to notice that I feel uncomvortable and sometimes there’s even some pain in the wrist area.
This is basically how your hands are positioned while typing:
When I was a little kid, I used to play piano. Of those time only few things are left: I don’t rest my wrists when using keyboard. Most of the time my elbows are also in the air, but that depends on the table and chair having right heights.
I prefer when keyboard upper rows are higher then the lower ones - that makes it easier for me to reach them.
And I lift my right hand theatrically after hitting an enter key
Despite of two decades of mouse-clicking and keyboard typing I have not developed any wrist or elbows problems :). Pianists do have their keyboard use system well thought out.