That seems pretty reasonable, yes. That is like asking if putting a low-cost Ops Research specialist in every company could make a 5% difference in operations - yes it could. Making resource-efficient decisions is not something that comes naturally to humans and having a system that consistently makes high quality game-theoretic recommendations would be huge.
Bunch of tiny companies would love to hire a mathematician to optimise what they are doing to get a 5-10% improvement. Unfortunately a 5-10% improvement in a small business can't justify the cost of hiring another person, and good mathematicians with business sense and empathy are a rare commodity.
Lots of jobs like daycare, teachers, cleaning, the material costs are near zero and your ability to increase productivity using technology is very low.
You can reduce quality of cleaning. But it's very hard to clean faster and better at the same time.
These industries are not going to be optimized by an AI. The only optimization is lower overhead or lower salaries.
Sure, we could have robots in daycare, but I don't think lack of AI is why my wife would have concerns :)
If that seems reasonable to you then you don't know anything about residential construction. The problems that homebuilders face aren't amenable to mathematical solutions. They have to deal with permitting issues, corrupt / incompetent government officials, supplier delays, bad weather, flakey workers, etc. The notion of a 5% improvement from LLM is ludicrously naive.