Cryptogram with one frequent letter and other letters random

I arrived at this ciphertext as a result of a particular decryption step from the famous unsolved "Kryptos 4" cipher. It has a very unusual letter distribution:

?QGIYWJUJEAOKGOTKKCGGXGMYPLTOYGFNOPIOZPOMBLOQCCWT
?DONNIOHBRXBMEFJAOXOOLXETCQEYNTZPMFUNENWXOWXFLYRZ

Out of 98 letters, it has 13 O’s but no more than 6 of any other letter. The remaining letters appear to occur in a normal random distribution: 6, 6, 6, 5, 5, 5, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 2, 2, 2, 1, 1, 0, 0, and two ? letters. Does anyone have an idea about what type of encryption method may have produced such an unusual letter distribution?

The two letters that do not appear in the cryptogram are S and V, so the very frequent O’s and the lack of S’s make me think of Morse code, but I can’t find or think of any encryption method that could have simply resulted in 13 O’s, no S’s, and normal random distribution of all other letters. Any ideas?