They don't want to risk someone coming for a job, getting fired and becoming a drain on the social safety net. Able to care for themselves not just now, but for a while. It's a reasonable position.
For the government, the cost for any worker in the same circumstances would be the same. On the other side, the foreigners cost less to the government overall when they were educated and raised elsewhere.
I’m not saying you are wrong, just that the previous rules are already in place in that very direction, and the changes are being placed instead to please and gain political support.
So while it's very rational to demand strong language skills, and very rational to expect people to go with a certified school given the unique difficulty of the language, potential residents are essentially limited to earning part-time wages (typically much lower than full time) during that period, and virtually barred from proactively engaging in any other kind of economic activity. They could transition to a business manager visa after that, but it will have to be a new business set up from scratch which must include at least one Japanese hire as well as minimum language skills; essentially requiring business activity/know how and business planning which the person was barred from doing during the language acquisition phase.
It's not impossible to meet these criteria by any means, but it actively discourages bootstrapping and efficient use of available time.