It is possible that Trainline are being extremely optimistic in their investor announcements with regards to the FY2026/forecast £150m revenue loss, but because it's the stock market, they presumably have some basis for making that estimate, even if they don't reveal what that is. You can't make outright false claims or projections.
My understanding is that the delay is as much an issue with staff (specifically SMEs) at the relevant TOCs/RDG - just as much as data and the TfL cyber attack. Although I think the data issue is also a consequence of the people. People are taking early retirement, pay offs, secondments to GBR all over the place, and a lot of specialist knowledge is being lost or diluted. It's not just ticketing where this has had a major impact, pretty much every project from lineside engineering to new rolling stock is affected.