Ashura did nothing in those 20 years besides rob and be in despair over Oden´s loss, the dukes had no training confirmed.
The only confirmed to train is Denjiro, and he was toying with two sword Zoro during Yasuie´s execution.
The only confirmed to train is Denjiro, and he was toying with two sword Zoro during Yasuie´s execution.
Very unlikely, especially when both he and Inuarashi pointed out to Kin'emon that they had 20 years to become stronger. They certainely did some training and had some battles to better their skills.