Re: "psychosomatic illness"
I.e. hypochondria. Or actually, given the transmission vector of this particular disorder, it'd be more appropriate to diagnose it as mass hysteria.
As for gluten-free haggis and black pudding, neither recipe is supposed to contain wheat anyway, so the fact that explicitly "gluten-free" versions are available is a bit comical.
The reason for the gluten-ified bastardisation of this or any other type of sausage is usually the unwarranted addition of rusk, a cheap filler material used to "bump" any sort of stuffing mix, solely for the purpose of ripping off customers.
This was such a huge problem in the past, most typically with pork links sausages, that the government actually had to intervene and force sausage producers to meet or exceed certain minimum proportions of the primary ingredient before they could legally sell it as "meat".
As far as I can tell, the last bastion of legacy "mostly rusk not-really-sausages" in the UK exists only in Northern Ireland, which sells what they refer to as "white pudding", a dish that bears no resemblance whatsoever to its namesake on the mainland, but is really just a poor-man's "pork" sausage. They manage to get away with this simply because they refer to it neither as pork nor sausage, although that's really what it is, albeit in its absolute minimal form.
However, bumping processed "meat" in general with rusk (and many other things - primarily water) is sadly very common, albeit heavily regulated to ensure that consumers receive something that is mostly meat.
I believe that Stornoway Black Pudding is widely recognised as the best in the UK, and contains no wheat at all as per the traditional recipe, not because the producers are pandering to hypochondriacs.