On Yamaha PSR models prior to the PSR-9000, 740, 640 (e.g., since about a year ago), we only had AB variations. It is only on these newer models that we now have ABCD variations. Thus, the vast majority of user styles and most internal styles in circulation only have AB.
Additionally, at our egroups site, people have made conversions of the ABCD styles for the newer PSRs to AB for the older ones. Anyone who wants to do EMC conversions for the X-1 so it will have ABCD should make sure they are using a set of new styles that have not been converted from ABCD to AB.
Thus, it is likely the styles you are using on your X-1 are only made to have AB.