Sure it's a little generalized to say Android 4 is a tablet -
but in 80% of the cases this might be a hit - the other 20% are rather a minority :)
This is a theme developer tool, for more precise detection one should use a custom browsecap.ini ... or switch mobile clients by .htaccess already.
By JS one can easily calculate available screen an it's aspect ratio.
There's not too many plugins around capable of pushing content through a few different themes - at the same time ... which is the main application.
Besides a better patch might be to change the regex to include the required 1 device (that pattern just matches my devices, feel free to modify it according to your environment).