Perhaps the carbine was easier for the Koreans to handle?
When the M-16 began to replace the M-14 in the U.S. Army around 1967, our South Vietnamese allies received M-16s to replace the Garands they were carrying & it was said that the short statured Asians appreciated the lighter weight of the Armalite.
As for South Koreans, I don’t know. Sure hope their maintenance standards on Garands are up to par.
I have a Garand which I built in 2000 on a newly made M-1 receiver & imported parts kit. It’s fine but I would like one that is 100% mil spec.