I think people might be a little confused about what the government is telegraphing here.

Japanese labour regulations are very strict, in particular around hours worked. Basically all employees (yes, including engineers) need to clock in and out, the concept of a "salaried worker" doesn't really exist, although normally engineers are paid for a certain number of hours regardless if they are actually worked. Primarily it is to make sure that overtime is paid and not excessive, but I believe there are also some related to the definition of what a "full time" job is.

So, it sounds to me like the government is considering relaxing those definitions on minimum hours worked to make it easier for firms to adopt 4 day work week if they so choose.