Clearly they're against DIY gas work and probably if you were a CORGI inspector who got to see some of the horrific 'DIY' (in the pejorative sense[1]) installations that they get to see investigating bad installation work[2] you'd take the opinion that as a general rule DIYers and gas are a bad combination.
[1] I recognise that there is a pejorative use of the term "DIY" and I use it myself sometimes (usually qualified by saying I'm using it in that sense) to describe some of the crap work of all sorts (not just gas) I see in people's houses. For example one of the teachers at my son's school bought a house which had an electric shower which one day spat out sparke from its casing while she was showering. On investigation one of the gems of that installation was 6mm^2 T&E joined with a choc-block, completely un-strain-relieved and un-enclosed in the attic. [2] a rogues' gallery of which is one of the highlights of 'Gas Installer' magazine. Examples include gas appliances hooked up to the supply with garden hose and jubilee clips and boiler flues extended using sections of tin can. The exhibition includes examples of builder's and others' dodgy works as well as 'DIY'ers'Indeed. Did you know that 87.5% of statistics are made up? ;-)
What you're seeing is the PR side of CORGI. What I see is their professional side. Unfortunately technically proficient bodies with inane PR and/or management are not uncomon.
If the HSE isn't big and ugly enough to evaluate lobbying from whoever then it's them you should be complaining about, rather than blaming CORGI and other groups for nott pussyfooting about in pressing their case.
Google 'crapita'.