I'm lucky enough to know both Rob and Julian personally, but this definitely doesn't serve as an excuse not to re-read the Mom's Test.
Very good point about the ICP. We were targeting startup companies 20-250 ppl, that raised their last round in the last 6 months, sector agnostic. However we weren't sure about the right decision-maker. The three options are CTO, CEO and HR manager.
So far we had more top-of-the-funnel conversions on Linkedin ads from CEOs and HRs, but more actual sign-ups from CTO.