After 1905 when Japan defeated Russia, Chosun practically ended. 
What happened in 1909 is the act of Japanese government. So, 

it must have been part of Japanese ruling even though the professor 

is not saying it. 

Yes, indeed, I heard, doc, Japanese implied same law(?) to every Korean as well, having the last name as the way Shogun did to Japanese to give the name to every child to encourage the child bearing whenever and wherever to restore the man powers after it conquered whole country to stop the killing among the local war lords. So you are right. Japanese did it all,  buddy.

Anyhow, I also heard that quite a few well-known family 종손  became rich by selling the 족보 to let the lay people to claim/legitimize 양반 class in these days!!!! What a country!

BB Lee