IMO Auto 'Select Subject' is not "Magic" unfortunately. The AI that finds the subject may not work on all images.
It is suited to subjects like 'portraits', or images where the 'subject' is singular, and contiguous, with good delineation.
Detailed subjects, as your windows, do not suit the Select Subject Masking.
Example- my chairs! Auto Mask also finds the grass behind the chairs-
Sometimes a Giant Brush, with [Auto Mask] turned on can select areas (such as window panes) with just ONE click of the Brush on an appropriate 'tone'.
Regards. My System: Lr-Classic 12.2 Photoshop 24.2, ACR 15.2, Lightroom 6.2, Lr-iOS 8.0.8, Bridge 13.0.2, Windows-11.