It is really really hard to find good lumber anymore, and the engineered fingerjoint studs are IN MY OPINION, a better product for rough framing purposes. A solid piece of lumber has the disadvantages of twisting and warping, while the engineered boards, in my experience, tend to be joined so that the grain directions are alternated from section to section. The wood still warps, but because the individual sections alternate, the warpage tends to be cancelled out. Most framing of this type is in compression, and I would not recommend a fingerjointed stud in a tension member, but there shouldn’t be very much of that in your home except in the roof trusses, and hopefully they are manufactured off site.
The builder should have mentioned these things to you when he “changed his position”, but he’s not wrong, and I don’t think you are being baited and switched.
The things I would actually look for are electrical compliances, grade compliances, etc. Things that really matter.
good luck
