The utility discs are Magic Gate encrypted so they only work on a console that matches 100% the intended region.
While a Japanese utility disc is branded NTSC-J it will only boot on a Japanese console. Any other NTSC-J console will get a "PlayStation 2" logo and a black screen afterwards.
That's the origin of the folklore that utility discs don't work when modchips are installed. What doesn't work is cross region booting.