Reasonable, but they're going about it in irrational ways. For example, a person on a student visa is allowed to set up a company in Japan, but technically they're not allowed to put in any hours managing it. There's a strict 28-hour/week working limit, and a person is allowed to operate as a sole trader performing very specific tass, but the moment they rent an office or hire an employee they're in violation of their visa.

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.