Thank you Jonny! Nice research there! I downloaded the style converter software and installed it.
The parameters are suspiciously similar to Yamaha's Style File Format (SFF), except that this software gives you direct access to some elements of the CASM which are not accessible in Yamaha's hardware arranger menus, and were previously only editable by other third-party utilities. The resulting file is saved with a .STY extension (which is what Yamaha uses.) I tried it in my BK9, and even after renaming it with an .STL suffix, it would not play. My Tyros is put away so I couldn't try it on there, but I suspect that it's a Yamaha style file with a Roland-specific "header."

This copy-catting isn't a terrible thing. Yamaha's parameter set for transposing the stored pattern was WAY more complete and mature than Roland's. For example, I had lamented the lack of a "retrigger" option on Rolands for a long while. If it's true that earlier E-X series keyboards were made by Medeli, that would affirm the use of borrowed Yamaha logic. I observed a while ago that the top of the line Medeli's also seemed to use Yamaha's style format and chord fingering.

Unfortunately nothing about this new keyboard or its style converter program provide any benefit to veteran Roland players, who are used to the Roland chord fingering and hoping for a BK-9 successor. Heck, I can't even recommend it as a good beginner keyboard. After reviewing the videos and owners manual, it apparently lacks an option for Bass Inversion, i.e., there is no way to play "slash" chords! The Yamaha PSR-E473 also lacks any control of bass inversion. That leaves the Casio CT-S500 and CT-X3000 as undisputed king in this price range!