German heavy-gun plans and the space taken by sliding breeches

Wouldn't Germany have investigated 14-inch guns because of the treaties?

The planned H-class guns were 16-inch, while their development status remains uncertain.

German plans did include 16-inch guns for the H class, although how far their development had progressed remains debated. The fleet otherwise stayed largely with 15-inch guns. A separate objection concerns the space occupied by sliding breech mechanisms. Their engineering advantages are acknowledged as possible, but the practical criticism here is their bulk and the difficulty of operating them in confined arrangements.