Beg to differ, but the statute does not make it all clear what the facts are because,

A declaration of choice has no legal bearing on foreign citizenship.
There is no legal mechanism in place to require a person to make the declaration of choice other than a written notice from the Minister of Justice, which has never been issued.
Even if a person makes the choice there is no requirement to actually renounce citizenship and only a requirement to endeavor to do so.
In most cases it's legally impossible to renounce foreign citizenship if the reason for doing so is to comply with the Japanese requirement for choosing a single nationality.