I have not been on-board a SeaPiper (hint, hint)and doubt if I ever will have that opportunity. Their strong point is ... trailerable??? Perhaps it is the US's attempted entry into the 'narrow boat' community???
It is a purpose built boat and unfortunately some owners' may try to exceed the 'purpose'. That is their decision.
I've never been on a SeaPiper either, and doubt I will be (unless one makes its way to a boat show somewhere in the northeast or New England).
I agree with you that it's a 'purpose-built' boat. All boats have compromises (those pesky laws of physics and limits of engineering), except maybe Jeff Bezos' yacht (for half a billion dollars, you can bend the laws of physics).
As you said, the SeaPiper is a 'narrow' boat (as well as shallow draft). Perhaps trailerability is a key marketing advantage, but 'narrow' boats also can be more fuel efficient than the typical big, beamy, boats most people favor for their spacious interior room. Even for a full displacement boat, the SeaPiper gets by with small power (85 hp), resulting in sipping fuel rather than guzzling. But there are trade offs for parsimonious economy. As there always will be.
It will be interesting to see if more fuel-efficient 'narrow' designs make their way to the market and what the demand will be for them, given the new reality of diesel fuel likely staying above $5/gal for the foreseeable future (meaning, the rest of my life).
This Sam Devlin design looks very intriguing to me. 48 ft long, 11 ft beam, 14 kts cruise on 225 hp at a claimed 4.4 gph:
https://devlinboat.com/blue-fin-48/
It might be technically a 48 ft boat with the interior space of a typical 36 footer, but it's a very appealing combination of attributes (though with the trade-offs of having to pay for a 48 ft slip, and I wonder how 14,800 lbs will handle rough waters).