Which is why there are Solution Architects who are (hopefully) familiar enough with the technical and business side of things to provide a high level solution o

Which is why there are Solution Architects who are (hopefully) familiar enough with the technical and business side of things to provide a high level solution overview and maybe a POC that will play into the scoping of the SOW. Also helps if the same ppl who estimate (architects/PMs) then end up being in charge of the project delivery. This will keep them honest and prevent severe under-estimations while keeping them on the hook from over-estimating provided that there's an internal review process for the estimates.