He’s wearing SMG mag pouches, which does tend to suggest that the Bren was a very short-term acquisition. There is another famous photo of German troops at Arnhem firing at British aircraft with a captured Bren (which is mounted on stacked ammo cases!).
From a soldier’s point of view, the best weapon was often the one that was lightest, most reliable and easiest to clean. The author George MacDonald Fraser described how, having been promoted to L/Cpl, he threw his newly-issued Thompson into a Burmese stream as soon as he could find a .303 rifle to replace it - the Thompson was just too damn heavy and prone to rust! Those factors far outweighed the firepower advantage. Similarly, Robert Morgan of the US 327th Glider Infantry Regiment, describes how he ditched his BAR for much the same reasons.
It does make me chuckle when my cadets, whose experiences of WW2 weapons goes no further than playing Call of Duty, often tell me that they would choose a Thompson or BAR over any other weapon… Of course, they’ve never had to carry one (or its ammo) or clean it or fire it.