From our experience, marginal. Our kids have only started using the brake [much] after they were already capable of pedalling a 'proper' bike.
On the other hand there has also been a year or more of overlap when they could use a pedal bike, but still had a lot of fun on a balance bike too. In those years they were making much heavier use of the brake on the balance bike.
Once they were that bit older but still using it, the brake was pretty effective (Ridgeback Scoot in our case). Not so much when younger. Maybe the strength and coordination arrive at similar times?
[edit] To put ages on those:
Soon after 2: Enjoying the scoot, but definitely not using the brake.
After 3.5 ish: Pedalling, using brakes a little.
Nearly 8: Still enjoys balance bike when she can get to it before younger siblings. Easily skids the rear wheel with brake.