@Moridin69 now, them being impressed is important. Tool technology has developed so far that you take it for granted. Tools sucked dick when we had no level of percision, ability to easily make and manufacture metalic items. Being able to prepare lumber and all that is pretty tough too. Metal was very expensive back then and was reserved for weapons, some farm tools and mostly something the rich only had. With our metal presses which can easily stamp out thin steel shovels with ease is probably 800+ years away even with his help unless they got lucky. If they made shovels out of metal I'd bet they'd be thick heavy and they wouldn't last long. They would rust away.
The author seems to have done research on tools and technologies from the period that they are placing this planet. Heck their firepit they use has an interesting invention used in Europe well over a 1000 years ago. That twig holds the pot what that thing piece of wood acts like a prop and the rising air turns the prop and the pop making the meat, pot or whatever they are cooking gets heated more evenly.
What the MC is doing is kinda destroying a people by artificially increasing many aspects of the country that would most likely flop a short while after he is gone for good. Their foods do well mostly due to the stuff he brought from japan. Books are probably the only safe things to bring for the most part (imagine the languages are the same) and they re-imagine the tech and reverse engineer it themselves would mean they are building themselves up even if they are using the knowledge of others. So long as knowledge is stored and shared it can't really fuck them in the end. The world is further back than I initially thought if they didn't have something like a water wheel already, not for aqueducts as that would take more brains, but to use them to help process grain