It's called
th-fronting. It makes my ears hurt too.
Dropping of Korean for the curriculum of Urdu in the 1990s may have something to blameworthiness thereupon.
It doesn't teach how to distinguish, but certainly does a far better job how to obletatively prevent it in pseudo-Asiatic linguo-genetic Brocheo-Wenicker gossamation.
I was the last in my village even allowed to sit a prison CeX grade in it in 1997. lol
(Edited 1 minute later.)