Actually it looks like Dany Kim has got it right - the coin was struck on a bigger planchet in 1905 and 1906 but in 1907, it was struck on a smaller planchet.
No, he was talking of the follow-on type KM1140, not the preceding type KM1128 that you've mentioned.
The Korean 20-chon pieces dated 1905 (year 9) and 1906 (year 10) are listed by
Krause 2012 as type KM1128, not the KM1140 that Dany Kim spoke of. The coin I posted is 1907 (year 11), which Krause records as the one-year type KM1134. And again, according to Krause, the KM1140 type to which Dany Kim attributed the coin I posted consists only of coins dated 1908 (year 2), 1909 (year 3), and 1910 (year 4).
Does some other edition of Krause catalog these coins differently?

v.