Not necessarily.
Dresda used 1/4 plate IIRC. Obviously Degens preferred the lighter weight material but he also said that 3/8 alloy, or steel, vibrated more.
Far more important, is to allow more material in the vertical plane. For example, most Pre Unit Triton engine plates break the rear gearbox plates, either through the adjuster slots or because they taper too much where they meet the top rear frame mounts. Adding depth in these areas solves that.
Unit construct plates of the design shown in this thread will NOT break unless they are fitted under tension and submitted to excessive vibration.