The “watchdog” is the UK’s National Infrastructure Commission, which is staffed entirely by civil servants, and whose remit covers far more than domestic heating. Not sure I see a link to the heat pump industry.
If anything, the opposite is true - the Energy and Utilities Alliance (who are quoted as being pro-hydrogen) is an industry body comprised of gas companies and boiler manufacturers, some of whom are selling boilers branded as “hydrogen mix ready” despite the UK having little to no infrastructure to distribute hydrogen at scale.
The "watchdog" group is an organization founded by Tories, and the lead guy is probably there just because he's tall. It's not a credible organization.
Look at the list of commissioners and their credentials. Many are economists but there are several civil engineers and even an Oxford professor who is a former director of the Environmental Change Institute. Mostly they seem legit.
I’m as happy to go Tory-bashing as most, but let’s at least make our disdain evidence-based.
Not everyone is on the same page as the leadership of that group. I'm sure if they did a real poll of all experts there, many will disagree with the leadership.