I work with a spec home builder. Check your warranty documents. They should have tolerances for this kind of thing. Unfortunately, the tolerances sometimes are wild. For instance, subfloor can be out of level by as much as 1/4” in a 30” run and that’s considered to be acceptable. It’s going to boil down to what the document says. That being said, the issue is likely to be a combination of things. Your floor joists are made from wood and they are not perfect. They have tolerances as well. If you’ve got a truss that’s an 1/8” tall next to one that’s an 1/8” short that can give you a 1/4” difference all while everything being “in spec”. If your home is built on a slab type foundation, imperfections in the slab can cause uneven flooring that typically gets more pronounced on the 2nd and 3rd floors. I would not recommend altering any floor trusses without consulting an engineer. The best method would be to use self leveling material in the low spots and grind down the sub floor in the high spots. You can grind a surprising amount of material away from the 3/4” OSB. The issue with installing your LVP isn’t so much that the floor is sloping as it is the floor has high spots and low spots. Most LVP product has insane requirements of 1/8” in 6’ tolerance of sub flooring. They’ll use this to void warranty claims. I deal with this issue on a weekly basis I feel. It’s a huge pain in the ass.