Applying for ILR after 3 years in Academia

Hello everyone, particularly those who have successfully applied for Indefinite Leave to Remain (ILR) under the Global Talent Visa (GTV) route. A colleague of mine was endorsed as a cybersecurity expert during the second year of his PhD.
He is now preparing to apply for ILR but is unsure whether he can use his earnings as a Senior Researcher at UCL as part of the evidence for his application. Specifically, he is concerned about whether his income from academia would suffice or if he would need to secure a position in the industry and provide at least three months of payslips from that role. Could anyone with experience in this process share their insights?