[Arran]

Mr Fix;
Part of the reason for the low tube count in that Kolster-Brandes was obviously for battery life, but the other reason was that the B.V.A charged a "license" fee of 1 pound per valve. There was also apparently a silly stipulation that a valve could not have more then one section on the same envelope, but I think that may have ended before the mid 1930s. So they used to employ tricks like regeneration, and reflex circuits, things that were basically gone in U.S sets by the mid to late 1920s as tube prices came down, and AC sets took off.
I have noticed that Philco seemed to design circuits around patent royalty avoidance, like the infamous "autodyne" oscillator-mixer circuits, the model 19 and 89 seem to be based on this reasoning as the Model 60 debut in 1933 and used a proper pentagrid convertor 6A7. The set you mentioned I have had a few, basically city sets, the gain on one I have is actually not bad, but the selectivity is not with only a two gang tuner, they are the type that sold for under $10 in some cases in discount stores.
Regards
Arran