I agree with Noflymore - I flew as a test pilot on a PPL quite extensively - but was employed as an airworthiness engineer.
I did do a CPL, as much as anything before anybody asked the sort of questions being asked here about TCT, about me. I've certainly been glad of the CPL, which opened other doors, and gave me additional knowledge and skills I've used extensively, but it's not clear that I ever strictly needed it.
And, frankly, there's quite enough already to criticise about TCT's integrity, it's not a useful addition.
G