The AI analyses sample data from old and new system, and then builds a prototype deterministic mapping pipeline. The experts can then inspect said pipeline and with their domain expertise catch edge cases/exceptions/uncovered cases, fix them and improve things, and then you use the vetted deterministic pipeline for migration. Yet, the initial AI draft saves enormous time.
But the problem identified that is talking to people and having them record data.
The stack certainly could need improvement, but much of the overhead comes from the process being pretty serial because each step depends on the previous. If someone we needs to talk to goes on vacation, sick or has a full calendar this delays it much further. Iteration speed is not linear in such cases. We do a lot of custom solutions and have to implement custom parsers or interface with undocumented ancient software or simply no existing software. Everything is custom, because previously they have no processes, no IT infrastructure or simply only data intended for humans (roughly structured, informally written, ever changing naming schema, typos).
This area is one which AI has shown to be pretty good (as long as some error rate is acceptable). Character recognition, voice transcribing, converting documents from one standard to an other. I can see an argument that if people spent most time doing those things, AI will speed it up (with a bit of added errors).
I am reminded however that in translations and AI generated subtitles, there is still a lot to be desired compared to the human touch. Handwritten papers in a different language, using local short hand and assumptions, may result in some odd and error prone AI transcription.