You probably recall that when the Czech Ultimate Edition was announced in this forum back in August, it was originally going to be a 2 disc set. The first disc would contain all three cuts of the film (Theatrical, Director's and Roadshow) with seamless branching, whilst the second disc would contain the bonus material.
The release was going to be the same as the US Ultimate Edition but with the addition of further language soundtrack and sub-title options, including Czech.
In the event, Fox decided, on grounds of cost, to only provide English soundtracks for both discs. The bonus disc was provided with multiple sub-title options, including Czech, but not the main disc containing the three cuts of the film.
Not a problem for someone who speaks English but a big problem for anyone who doesn't. Since this was a release specifically for the Czech Republic, it posed quite a headache for the local distributor, Bonton Film, since they would be trying to market it to a customer base whose first language was Czech not English.
Their solution to the problem was to include an additional disc, the previously released Czech disc, which included multiple language soundtrack and sub-title options, including Czech. That disc, however, only contained the Theatrical Cut. Although the Blu-ray releases in North America and Western Europe had been of the Director's Cut, for some unknown reason, those in Eastern Europe and Asia had only been of the Theatrical Cut.
It's for that reason that the Czech Ultimate Edition became a 3 disc set, as opposed to the 2 disc one originally announced. Obviously, for an English speaker, the additional disc of the Theatrical Cut is superfluous since the Theatrical Cut is also contained on the main disc, alongside the Director's Cut and Roadshow Cut. For a Czech who doesn't speak English, however, the disc of the Theatrical Cut is essential, as it enables the viewer to watch the film either dubbed in Czech or in the original English with Czech sub-titles. Those Czechs who can speak English, of course, can utilize the main disc to view whichever version they wish.
As an English speaker myself, the additional disc of the Theatrical Cut is redundant but I'm actually glad that the Czech release contains all 3 discs, since it makes their edition unique. It's certainly preferable to the Korean one where the new disc containing the 3 cuts was completely jettisoned and replaced with the earlier disc, containing only the Theatrical Cut. How they were able to get away with still calling that an Ultimate Edition is beyond me.
So, you'll see from the above that the inclusion of the additional disc was nothing to do with image resolution and bitrate but simply a case of trying to make the best out of the bad situation they found themselves in.