My anecdata isn’t so specific, and supports the bias of the claim:
In the early 2000s I spent a cumulative ten months out so bicycling along Japan, attending graduate school, and being well-cared-for by strangers (I’m a male from the US with Western European ancestors). Several hosts who had ancestors from the mainland (Korea, China) said life in Japan was the more difficult for it.
They don't speak to the particular law, but they are speaking of the patrilinear transmission of Japanese-ness. I'll keep digging - my source was a Zainichi family in Japan in 2004.
