I think DRP has it exactly right, without putting exact numbers on the problem. When you raise the ties you increase the tie tension forces (thrust reactions) for equilibrium of the roof system, thus making the tie to rafter connection more difficult to make adequately and more likely to be a failure mechanism. This higher tie also induces new axial and bending loads into the rafter, which causes it to need to be increased in sized. The cleanest and most direct load path solution is to make the ridge beam a spanning member, and to treat what had been low slope rafters as simple beams spanning from the ext. wall to the ridge beam. They no longer cause a thrust, so the large thrust problem goes away. By the way the rafters are cut or fitted, they only apply vert. reactions to the walls and the ridge beam.
I think I understand ICE’s or DRP’s builder friend’s thought process, and it goes something like this: if you can only make the rafters act a little bit like normal rafters, they will either impart less reaction on the ridge beam, or actually act like a normal rafter and actually balance and support the ridge beam (now a ridge board); in either case you should be able to reduce the size of the ridge beam, maybe only to a ridge board. However, the rafter/tie connection can’t be desinged/built half way, it slips/yields a little, allowing some rafter spreading and putting more vert load on the lighter ridge beam, which deflects some more; which causes more spreading of the rafters, or higher tie tension and finally, I would bet on the tension tie/rafter connection failing. These members and member sizes and connections can be made to work, within reason, but they are just not normally practical. This is akin to a very flat sloped truss, which really act like a beam, so design it as a beam or parallel chord truss; or akin to a very flat arch which has such high thrusts that it becomes an impractical load carrying system.
Structures don’t act like you wish they would act, they act the way your design and detailing force them to act, and they are smart enough to know how they must act. You can’t fool them, but they sure as hell can fool you, if you’re not careful.