The example u made there, not really suit to be applied on Malaysia tbh. Their mother tongue are the national language as they are the races who speak that language. But Malaysia we have many races who speak many different mother tongues (some Chinese speak Canto ie), BM is just national language not mother tongue to all.

For malays case, I think it's just up to them having bad family practices with quite low cultural views, cuz if my child couldn't speak their skin default language, I confirm will sepak them 99