Correct - the auto-detect hack overrides any user style choice and enforces styles as configured with in the addon.
The thing to bear in mind here is that the mobile autodetect hack is a stand alone product. It has no dependencies on styles and has nothing to do with this style or it's add-on.
Now to your questipon regarding this style and the the 'Mobile Style Options' (lets call it MSO for short) add-on which goes with it.
MSO is tied to this style, it was written so that some minor changes could be made to the style which did not rely on people having to make manual template changes. The thead for MSO is here:
https://vborg.vbsupport.ru/showthread.php?t=182692 and details what it does. It is not a requirement for this style, it just makes customising a few options easier to do.
Specifically, MSO asks
What is your Mobile style? so it knows which style it is meant to work with and how to apply options such as hiding mobile style from style chooser and adding 'Posted by Mobile' text.