I did a very quick image search for wartime 25pdrs....
I found quite a few undated pics that appear to be wartime, featuring muzzle brakes on the guns.
But theres no way to verify what you are seeing in these photos,
so I won't reference any of them or argue the point based on those photos.
Since this equipment stayed in use long after the war, there can be no argument
that Guns of this type were in service and equipped with muzzle brakes.
Canadian too!
And even though they were only used in training after that, its still valid.
So I am happy with that.
